Cold, member making ascent (5)
I believe the answer is:
climb
'ascent' is the definition.
('climb' can be a synonym of 'ascent')
'cold member' is the wordplay.
'cold' becomes 'c' (eg on taps).
'member' becomes 'limb' (limb is a kind of member**).
'c'+'limb'='CLIMB'
'making' acts as a link.
(Other definitions for climb that I've seen before include "What mountaineer does" , "Ascend - ascent" , "increase" , "Ascend, escalate" , "Scale or clamber" .)