Bond starts to uncover nefarious international terrorist enterprise (5)
I believe the answer is:
unite
'bond' is the definition.
(thesaurus)
'starts to uncover nefarious international terrorist enterprise' is the wordplay.
'starts to' says to take the initial letters.
The initial letters of 'uncover nefarious international terrorist enterprise' is 'UNITE'.
(Other definitions for unite that I've seen before include "Couple" , "Marry" , "Get together" , "Make one" , "Connect" .)