Love with no object (7)
I believe the answer is:
nothing
'love' is the definition.
(love means zero in tennis)
'with no object' is the wordplay.
'with' says to put letters next to each other.
'object' becomes 'thing' (an object is a thing or item).
'no' put next to 'thing' is 'NOTHING'.
(Other definitions for nothing that I've seen before include "Not a whit" , "Not anything" , "Something of no concern" , "What Cordelia had to say" , "Zero, nil" .)