Tail off (7)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
dwindle
'tail off' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for dwindle that I've seen before include "'Die down, grow less (7)'" , "become weaker" , "Degenerate" , "Die away" , "Diminish - shrink slowly" .)