Love is ... (7)
I believe the answer is:
nothing
'love' is the definition.
(love means zero in tennis)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for nothing that I've seen before include "Something sweet" , "Zero, naught" , "One of those sweet sayings" , "Not a whit" , "signifying love" .)