Member to ascend without leader (4)
I believe the answer is:
limb
'member' is the definition.
(member can mean a limb)
'ascend without leader' is the wordplay.
'ascend' becomes 'climb' (climbing is a kind of ascending).
'without leader' means to remove the first letter.
'climb' with its initial letter removed is 'LIMB'.
'to' acts as a link.
(Other definitions for limb that I've seen before include "Human's extension" , "Branch - member" , "Eg, arm, leg" , "arm, perhaps" , "Branch - arm - leg" .)