Conservative member's rise (5)
I believe the answer is:
climb
'rise' is the definition.
('climb' can be a synonym of 'rise')
'conservative member's' is the wordplay.
'conservative' becomes 'c' (abbreviation commonly used in UK politics).
'member' becomes 'limb' (limb is a kind of member**).
'c'+'limb'='CLIMB'
(Other definitions for climb that I've seen before include "Soar" , "Ascend, scale" , "Rise to a higher level" , "showing the way up" , "Get higher" .)