Alwayspuzzled, it took me a while to track down 29 A. You need a single letter abbreviation, followed by a word for 'group of friends' (more wartime, say, than at school). The latter loses its first letter, to fit the definition of the first three words.
26 D has only one change - to the word you have suggested! The 25 A change is at the end of the word. 27 A works ok too, and has just one change.
20 Is a fairly unusual word, I'll try to think of a hint or nudge!