Equal rent negotiated for associate (7)
I believe the answer is:
partner
'for associate' is the definition.
(partner is a kind of associate)
'equal rent negotiated' is the wordplay.
'equal' becomes 'par'.
'negotiated' indicates anagramming the letters.
'rent' anagrammed gives 'tner'.
'par'+'tner'='PARTNER'
(Other definitions for partner that I've seen before include "Companion at bridge, dance, or home" , "Ally" , "sometimes joining in crime" , "Mate or business associate" , "Mate or collaborator" .)