Infinitely large, definitely cryptic

Question

This is an infinite cryptic crossword. Solve the clues and use the four given grid pieces (each duplicated infinity times) to create a grid that continues endlessly in all directions.

Across
A1. Soldier that earns pay from sea in Ajaccio, Corsica's capital
A3. Crazed maniac? Her rant shows extreme depression (2 wds.)
A5. High frequency of broken heart during concert Zappa's leading
A6. Birds almost turn home and escape, maybe
B3. One missing from couple? That's standard
B5. Arguments for people getting paid
B6. Near stern judge (later president) William, Howard needs no introduction
B8. A tiny bird in action (2 wds.)
C1. Sending back gloomy music lover to a small island (2 wds.)
C2. "Dr. West?" – Looking towards West, Dr. King said he had one
C7. Fencing equipment is covered in the PE exam
D2. Shadow regularly covers edge of Bronx, New York state
D3. Whistleblower lost rank
D5. "Tatars possibly engaged in illegal activities" – article, NYT's cover
D6. Explosive device backfiring in increased rate, perhaps

Down
A1. Muslims initially request face covering
A2. Flying cars in Australian city
A3. One thousand milk products served up? That's a lot
A4. I moved to northernmost extreme in French territory to identify lizard
B1. Ultimately, Francis is not someone to be revered
B2. Harm evil entity with gas
B4. "The Living Daylights" – group of antagonists hunting agents' heads (hyph.)
B7. Radical extremists in Zimbabwe supported by many
C3. The unstable Yankee left compound
C4. Just retired, actor Irons undressed
C5. Pause speech for recovery
C6. A stand-up storyteller from Greece
D1. Former lover, according to a friend of Barney Stinson's, is upset
D2. Labourer and I escaped upcoming infernos
D4. Pianist Tatum's music?

Answer 1

The answers to the clues are:

Across

A1. -> MERC (Soldier = MERC (mercenary), sea in Ajaccio = MER, Corsica's capital = C)
A3. -> MARIANA TRENCH (anagram ("Crazed") of "Maniac her rant" - extreme depression = deep trench)
A5. -> GIGAHERTZ (concert = Gig, Zappa's leading = Z; anagram of heart between these two;)
A6. -> TURKEYS (TUR(-n) [almost turn] + KEYS [Home and Escape, on keyboard]) - thanks to Jeremy Dover for this one as I hadn't worked it out myself. B3. -> PAR (Couple = Pair, remove "one" (i) to get PAR = standard)
B5. -> PROS (straightforward double definition of PROS)
B6. -> AFT (AFT is near stern on a ship, William Howard tAFT with no introduction)
B8. -> AT IT (A bird = A TIT, in action = AT IT)
C1. -> SAO TOME (gloomy music lover = EMO, to a small = TO A S and then turn it all backwards to give an island)
C2. -> DREAM (Dr then MAE (as in Mae West) backwards, Martin Luther King famously said "I have a dream"
C7. -> EPEE (fencing sword = EPEE, the letters are included in thE PE Exam)
D2. -> SAXONY ("shadow regularly" = S A O, around X which is the "edge" (last letter) of the Bronx, and followed by NY for New York; Saxony is a state in Germany)
D3. -> NARK (anagram of RANK, meaning whistleblower)
D5. -> CRIMEANS ("illegal activites" = CRIMES with an article (A) and NYT's cover (first letter, i.e. N) included in it gives CRIMEANS who were Tatars.)
D6. -> PETARD (the letters of PETARD, an explosive device, are included backwards (backfiring) in increaseD RATE Perhaps)

Down

A1. -> MASK (Muslim initially = M, request = ASK, face covering = MASK)
A2. -> CAIRNS (anagrams of CARS IN, Cairns is an Australian city)
A3. -> MYRIAD (one thousand = M, followed by DAIRY i.e. milk products backwards ("served up") resulting in MYRIAD meaning "a lot")
A4. -> IGUANA (Take the I up to the top (Northernmost point) of GUIANA (a french territory) to get IGUANA, a lizard)
B1. -> SAINT ("Ultimately Francis" => S, is not => AIN'T, someone to be revered = SAINT)
B2. -> IMPAIR (evil entity = IMP, gas = AIR; IMPAIR means to harm)
B4. -> A-HA ("The Living Daylights" was an album by A-ha. first letters ("heads") of Antagonists Hunting Agents.)
B7. -> ZEALOT (Radical = ZEALOT, extremists (first and last letters) of Zimbabwe = ZE with many (A LOT) supporting (underneath) them.)
C3. -> ETHYL (anagram ("unstable") of "the" followed by Y(ankee) and L(eft) gives ETHYL, a compound)
C4. -> MERE (MERE = just, "actor Irons" = Jeremy, remove outer letters ("undressed") and reverse ("retired"))
C5. -> RESTORATION (pause = REST, speech = ORATION, recovery = RESTORATION)
C6. -> AESOP (A followed by "stand" (POSE) upwards gives AESOP the Greek author of famous fables / stories)
D1. -> EXASPERATED ("Former lover" = EX, "according to a" = AS PER A, Ted was a friend of Barney in How I Met Your Mother, and EXASPERATED means upset)
D2. -> SERF (infernos = FIRES, "I escaped" => remove I to make FRES, "upcoming" means turn it backwards and you get SERF, a labourer
D4. -> ART (Art Tatum was a famous jazz pianist, music was his ART)

The grids tessellate like so (the black image is the original four squares and then the red image shows how it lays alongside itself):