The Riley Riddle resolves to clue the board game:
My first can hold flags.
MAST - where on a ship one might find sails and flags.
My second lasts three months.
TERM - 3 months is a common length of term for a school or university term to last.
My last is your attention.
MIND and attention are synonyms of sorts.
My whole is the game you're playing.
Together (with overlap) they make MAST + TERM + MIND = MASTERMIND. But hang on... 'the game you're playing'?!
We're not done yet. Because as well as solving this riddle we are also actually playing a game of this! (This is what the mentions of 'accurate' and 'misplaced' 'matches' after each line refers to...) So let's solve the 3 cryptic clues too to give us everything we need...
10 thousand as 12.25
XMAS (12.25, i.e. Christmas Day) = X (10) + M (thousand) + AS
How The Beatles make Help relies upon just very beginning
RUJV = R(-elies) U(-pon) J(-ust) V(-ery). This (or possibly NUJV) is the word actually spelled out by the Beatles on their album cover for Help!:
They had originally intended to spell 'HELP' but it didn't look as great as they'd hoped from an arty point of view apparently...
Bend down for no points
DUCK - a double-definition for 'Bend down' and 'no points' (in cricket).
So altogether this gives us the layout of the board:
Here, 'B' indicates a black peg for an accurate (exact) match, and 'W' a white peg for a misplaced match.
We can now solve this to find the answer:
The first 3 rows reveal that there is no A, E, M, R, S or T in the answer. Row 4 then reveals the answer begins with 'X'. Rows 5 and 6 together reveal that the remaining letters must be D, C and K (no U), and with the help of row 3 we can confirm that the 'D' goes last, then the 'C' in third position and the 'K' second.