Defeat not in sport (7)
I believe the answer is:
outplay
'defeat' is the definition.
(I know that outplay is a more specific form of the action beat)
'not in sport' is the wordplay.
'not in' becomes 'out' ('out' is the opposite to 'in').
'sport' becomes 'play' (synonyms).
'out'+'play'='OUTPLAY'
(Other definitions for outplay that I've seen before include "As sportsperson, overcome" , "Get the better of" , "Act better" , "Defeat (sport)" , "Excel at games" .)