Cryptic crossword: ever more insensitive

Question

This is a cryptic crossword. All clues have the same definition, which has been omitted to avoid repetition so they consist of wordplay only. Solvers may notice some discrepancies between the lengths for the wordplay given in the clue and the available space in the grid; solvers are expected to find a suitable way of entering the answer that fits in the available grid space. Some clues refer to other clues, where the clue reference is given in parentheses (e.g. (13d) refers to the answer of 13 down). In the clue enumeration these 'lengths' are given by * to avoid making the clue enumerations look (more) ridiculous.

Two clues would normally require the use of punctuation symbols (specifically . or ,). This punctuation should be ignored for grid-entry, and the answers truncated appropriately.

When figuring the crossword out, solvers may find it useful to remember that ; is often used to indicate concatenation.

To obtain the check-mark, if anyone is still reading at this point, solvers must supply the completed grid, an explanation of the clues, and the (one-word) definition omitted from all clues.

Across

1. For example two feet, both as gnarled (6,2,3,5)
4. Pair of rivers lacking river; there's ten veins involved (3,6,8,6)
8. (19d) power, leader of lauded American couple; (13d) (*,4,3,*)
9. Vi boxed? (3,7)
10. Vicar, for example Irish Gaelic (20d); (17d); swirling ether; (17d) (7,*,*,5,*)
14. Sparta film; unlucky for some periods, (6d) belonging to me holding you and me just after (5,7,8,5,*,5,3)
15. Grind charged particle (7)
16. (6d) starts to mollify iatrophobic nurse using some (17d) without anybody (*,5,*,5,3)
18. Canvas shelter mixed up how few troop; a crowd (5,5,2,3,5)
21. Man alive followed by Ace, Ace and Ace (4,3,5,4)
22. 50% per record holding, each twelve months (4,1,4,4)

Down

1. Point west, for north is uncertain (3,2)
2. (19d) spells changed there (*,5,5)
3. Edge in exercise after last golf green (10,5)
4. Space-time flipped; (12d) venerated when seizing South (3,*,8)
5. Audibly consumed compositional element, initially including actual lasagne (5,9)
6. (13d) to arrange even sum... sin (*,5,5)
7. Grand ancient space rodent starts to invade Oslo (6,5)
11. Score honest diamonds (6,7)
12. (13d) plaza: Duke evenly applauds (17d) (*,7,4,*)
13. A mercy granted to Oscar. Fine, (11d) (3,7,2,*)
17. Post fourth first (5,5)
19. Joy after imago transformed (3,2,8)
20. "The fey folk" come after foxtrot (or tango) embracing unionist wife (4,7)

Answer 1

The missing definition is

NUMBER, as hinted at by the title, and this is a numerical crossword: all the answers lead to numbers which we must enter in (decimal) numerical form.

The completed grid:

Answers and explanations:

Across

1. For example two feet, both as gnarled (6,2,3,5)

NUMBER + (FEET BOTH AS)* = NUMBER OF THE BEAST = 666

4. Pair of rivers lacking river; there's ten veins involved (3,6,8,6)

TWO SEVERNS minus R = TWO SEVENS = 14; (THERE'S TEN VEINS)* = THIRTEEN SEVENS = 91.

8. (19d) power, leader of lauded American couple; (13d) (,4,3,)

(19d:21) P(ower) L(auded) US TWO = 23; (13d:100)

9. Vi boxed? (3,7)

SIX (Roman numerals) SQUARED = 36

10. Vicar, for example Irish Gaelic (20d); (17d); swirling ether; (17d) (7,,,5,*)

REV + ERSE (20d:48) = 84; (17d:11); ETHER* = THREE = 3; (17d:11)

14. Sparta film; unlucky for some periods, (6d) belonging to me holding you and me just after (5,7,8,5,*,5,3)

THREE HUNDRED (movie title); THIRTEEN (unlucky for some) TIMES (periods) (6d:93) [MINE holding US + ON (just after) = MINUS ONE] = 1208

15. Grind charged particle (7)

MILL + ION = MILLION = 1000000

16. (6d) starts to mollify iatrophobic nurse using some (17d) without anybody (,5,,5,3)

(6d:93) M(oll...) I(atr...) N(urse) U(sing) S(ome) (17d:11) MINUS ONE (without anybody) = 81.

18. Canvas shelter mixed up how few troop; a crowd (5,5,2,3,5)

TENT (HOW FEW TROOP)* = TENTH POWER OF TWO = 1024; THREE ('s a crowd)

21. Man alive followed by Ace, Ace and Ace (4,3,5,4)

FIVE (bingo) AND THREE ONES

22. 50% per record holding, each twelve months (4,1,4,4)

HALF A + LP holding EA + YEAR = HALF A LEAP YEAR = 366/2 = 183

Down

1. Point west, for north is uncertain (3,2)

(POINT with W replacing N)* = TWO PI = 6.283185[...]

2. (19d) spells changed there (*,5,5)

(19d:21) TIMES (spells) THERE* = THREE = 63.

3. Edge in exercise after last golf green (10,5)

P(RIM)E after EIGHTEENTH = EIGHTEENTH PRIME = 61

4. Space-time flipped; (12d) venerated when seizing South (3,*,8)

(EN T but the other way around) = TEN = 10; (12d:10011) REVER(S)ED = 11001

5. Audibly consumed compositional element, initially including actual lasagne (5,9)

EIGHT (sounds like ATE) FACTOR + I(ncl...) A(ctual) L(asagne) = 8! = 40320

6. (13d) to arrange even sum... sin (*,5,5)

(13d:100) (EVEN SUM SUN)* = 100 MINUS SEVEN = 93

7. Grand ancient space rodent starts to invade Oslo (6,5)

G + OLD + EN + RAT + I(nvade) O(slo) = 1.618033[...]

11. Score honest diamonds (6,7)

TWENTY + SQUARE + D = 400

12. (13d) plaza: Duke evenly applauds (17d) (,7,4,)

(13d:100) SQUARE + D + aPpLaUdS (17d:11) = 10011

13. A mercy granted to Oscar. Fine, (11d) (3,7,2,*)

A QUARTER (= mercy) O F (11d:400) = 100

17. Post fourth first (5,5)

I didn't figure this out, but fortunately @fljx did in comments below. FIFTH (post fourth) PRIME (first) = 11.

19. Joy after imago transformed (3,2,8)

(JOY AFTER IMAGO)* = AGE OF MAJORITY = 21 (which isn't the official age of majority in many countries, but is one age traditionally reckoned the start of adulthood)

20. "The fey folk" come after foxtrot (or tango) embracing unionist wife (4,7)

ELVES after (F OR T embracing U) W = FOUR TWELVES = 84

Credit where due: fljx figured out the wordplay for 17d which had completely eluded me, and also spotted a typo that I've now fixed -- and also kindly provided an image for the completed grid which is much prettier than the text-only version I'd previously had.