What for Don Juan stops fights? Bunches of flowers (8)
I believe the answer is:
bouquets
'bunches of flowers' is the definition.
(I've seen this in another clue)
'what for don juan stops fights?' is the wordplay.
'what for don juan' becomes 'que' ('what' in Spanish- Don Juan is a Spanish character).
'stops' is an insertion indicator (stopping can mean blocking a gap).
'fights?' becomes 'bouts' ('bout' can be a synonym of 'fight').
'que' put inside 'bouts' is 'BOUQUETS'.
(Other definitions for bouquets that I've seen before include "Bunches of flowers or pieces of praise" , "Compliments or bunches of flowers" , "Arrangements of flowers" , "Nosegays" , "Attractively arranged bunches of flowers" .)