Love's great - The End (5)
I believe the answer is:
omega
'the end' is the definition.
(thesaurus)
'love's great' is the wordplay.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'great' becomes 'mega' (I've seen this before).
'o'+'mega'='OMEGA'
(Other definitions for omega that I've seen before include "Greek long 'o'" , "in Greece, the limit!" , "Ultimate letter" , "Athenian character" , "symbol of resistance?" .)