Love being in the groove for overwhelming defeat (4)
I believe the answer is:
rout
'overwhelming defeat' is the definition.
(I've seen this before)
'love being in the groove' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'being in the' is an insertion indicator.
'groove' becomes 'rut' (synonyms).
'o' going within 'rut' is 'ROUT'.
'for' acts as a link.
(Other definitions for rout that I've seen before include "Runaway defeat" , "snore" , "Put to flight in disarray" , "Completely defeat" , "Put to flight, disperse" .)