Commit the new leader in an offer (4)
I believe the answer is:
bind
'commit' is the definition.
(thesaurus)
'new leader in an offer' is the wordplay.
'leader' suggests taking the first letters.
'in' indicates putting letters inside.
'an offer' becomes 'bid' (bid is a kind of offer).
The first letter of 'new' is 'n'.
'n' placed within 'bid' is 'BIND'.
'the' is the link.
(Other definitions for bind that I've seen before include "This weed" , "Tie, fasten" , "Tie together" , "Restrict" , "Tie up or hamper" .)