Peg wants to succeed for the most part (5)
I believe the answer is:
dowel
'peg' is the definition.
(a dowel is a wooden peg)
'to succeed for the most part' is the wordplay.
'to succeed' becomes 'dowell' (to do well is to have success).
'for the most part' means to remove the last letter.
'dowell' with its last letter taken off is 'DOWEL'.
'wants' is the link.
(Other definitions for dowel that I've seen before include "Peg to hold two pieces together" , "Wooden peg" , "Pin that holds two pieces of wood together" , "Cylindrical fastening pin" , "Peg for joining wood" .)