Doubt about chopped ice in packs for boxing (10)
I believe the answer is:
Here is my best explanation:
'boxing' is the definition.
('fisticuffs' can be a synonym of 'boxing')
'doubt about chopped ice in packs' is the wordplay.
'doubt' becomes 'if' (as in 'it's a big if').
'about' is a reversal indicator.
'chopped' means to remove the last letter.
'in' means one lot of letters goes inside another.
'packs' becomes 'stuffs' (**).
'if' reversed gives 'fi'.
'ice' with its last letter removed is 'ic'.
'ic' inserted within 'stuffs' is 'sticuffs'.
'for' is the link.
(Other definitions for fisticuffs that I've seen before include "fight", "Scrap", "Bare-knuckled fighting", "Fighting with punches", "Hand-to-hand combat?", "Pugilism", "Bare-knuckle combat" and "hand-to-hand combat".)