Liaison from date, not missing love (5)
I believe the answer is:
agent
'liaison' is the definition.
(thesaurus)
'date not missing love' is the wordplay.
'date' becomes 'age' (both can mean to get older).
'missing' suggests deleting specific letters.
'love' becomes 'o' (love means zero in tennis).
'not' with 'o' removed is 'nt'.
'age'+'nt'='AGENT'
'from' acts as a link.
(Other definitions for agent that I've seen before include "Business manager" , "Double-zero-seven, for example" , "Spy; representative" , "One does business on behalf of another" , "One may be working" .)