Love to talk back? That's fine (4)
I believe the answer is:
okay
'fine' is the definition.
(thesaurus)
'love to talk back?' is the wordplay.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'to talk' becomes 'yak' (yak is a kind of talk**).
'back?' says the letters should be written backwards (I've seen 'back' mean this).
'yak' written backwards gives 'kay'.
'o'+'kay'='OKAY'
'that's' is the link.
(Other definitions for okay that I've seen before include "Fairly good; approve" , "Alright" , "Informally, all right" , "Not terrific but acceptable" , "Passable" .)