Tender to win new contract (4)
I believe the answer is:
bind
'contract' is the definition.
(thesaurus)
'tender to win new' is the wordplay.
'tender' becomes 'bid' (synonyms).
'to win' indicates putting letters inside (some letters win or obtain others).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'bid' enclosing 'n' is 'BIND'.
(Other definitions for bind that I've seen before include "Impose a contractual obligation on (someone)" , "Senior figure" , "Join or fasten together" , "Wrap tightly - nuisance" , "Tie; problem situation" .)