The unclued lights (five of two words which include three apostrophes) can be preceded by the same word, all confirmed in Chambers and/or Brewer.

Across

11 A record bill, getting a pack animal (6)

12 Earthling beginning to excavate rock formation (7)

14 What contains oxygen and is able to girdle the Earth? (5)

15 Oddly, St Thomas in porticos (5)

16 Currency unknown to ethnic group abroad (6)

17 Jock’s meant to have decided without son (6)

21 Fabric dealer removes power from ambitious governmental worker (7, hyphened)

24 Moving into gear, I start (9)

29 Small change for...