Deliver on contract (7)
I believe the answer is:
release
'deliver' is the definition.
(thesaurus)
'on contract' is the wordplay.
'on' becomes 're' ('on' can be mean 'with reference to').
'contract' becomes 'lease' (leasing is a kind of contracting).
're'+'lease'='RELEASE'
(Other definitions for release that I've seen before include "press announcement" , "loose" , "New film" , "Authorise publication" , "put out" .)