Jo Not seen that abbrev before. It seems a bit confusing when some letters are known, and others like 3 and 4 would appear not to have. I was wrongly assuming that the suggestions were derived from what was for certain.
Tenth (decimal) Rate (assessment). I haven't got the puzzle but that seems to fit the clue. Of course, if there are interlocking letters to prove me wrong then I apologise.
There is a protocol on AB for crosswords. All the OP has to do is to supply the clue exactly as written together with the letter count and letters already placed, those unknown being replaced by ?
This way anyone who does not have the puzzle to hand can answer.