Twelve symmetrically disposed unclued entries comprise three distinct interlinked quartets.

Across

1 Precise conjecture about coin-flip, oddly (8)

6 Peter out back, eating square meal (6)

10 Hit round ring – rim of upper drum (6)

11 Tiny baby consumed by gas (7)

12 Pedestrian holds back directions to Wick (5)

14 Advert I tweaked late in development (7)

15 We animate Ferris wheels (6)

18 Legal excuses persist regularly, certainly on detaining leader (8)

22 No time for anointing abstract artist (8)

24 Petition Henry for backing Greek musician (7)

29 Opening cut by old, extremely delicate round swords (7)