Pledge bid on a tender as contracted (6)
I believe the answer is:
donate
'pledge' is the definition.
(thesaurus)
'bid on a tender as contracted' is the wordplay.
'contracted' says the answer is hidden in the clue.
'DONATE' is hidden in the letters of 'bid on a tender as'.
(Other definitions for donate that I've seen before include "Give as a gift as to charity" , "Give (money) to a good cause" , "Give (transplant organ)" , "Give to a charity or good cause" , "Fork out" .)