Greedy Kite....thanks.
Have I worked this out right ?
A Bread and Butter letter is a note sent to somebody, to thank them. Its an American phrase apparently, so not English as we know it.
A synonym for study could be READ and a synonym for group could be CLASS.
What I don't understand is I always thought that in cryptic clues, there should ba definition of the answer somewhere in the clue. But I can't see how anybody could have got BREAD AND BUTTER LETTER, if they didn't have any of the letters already.
I have prevailed on your kindness and patience long enough this morning, so thanks for your help in this. I can't be the only one who is confused surely ?