Heavyweights in defeat saved by endless cash (7)
I believe the answer is:
colossi
'heavyweights' is the definition.
('colossus' can be a synonym of 'heavyweight')
'defeat saved by endless cash' is the wordplay.
'defeat' becomes 'loss' (I've seen this before).
'saved by' is an insertion indicator (I've seen this in other clues).
'endless' means to remove the last letter.
'cash' becomes 'coin'.
'coin' with its final letter taken off is 'coi'.
'loss' put within 'coi' is 'COLOSSI'.
'in' acts as a link.
(Other definitions for colossi that I've seen before include "Very large statues" , "Giants" , "big figures?" , "powerful people" , "Enormous statues" .)