Quarrel that's quick blows over (4)
I believe the answer is:
spar
'quarrel' is the definition.
(I've seen this in another clue)
'quick blows over' is the wordplay.
'quick blows' becomes 'raps' (I've seen this in another clue).
'over' is a reversal indicator.
'raps' reversed gives 'SPAR'.
'that's' is the link.
(Other definitions for spar that I've seen before include "Box for practice" , "Engage in argument" , "Translucent mineral" , "supporting member" , "Raps with wooden beam" .)