Nought but love (3)
I believe the answer is:
nil
I believe this clue is a double definition.
'nought' is the first definition.
('nil' can be a synonym of 'zero')
'love' is the second definition.
(I've seen this before)
'but' is the link.
(Other definitions for nil that I've seen before include "Non-existent" , "Nix, nada, nothing" , "You get nothing" , "Latin zero" , "Nothing, no score" .)