Conservative member's route to the top? (5)
I believe the answer is:
climb
'route to the top?' is the definition.
(climb can mean a route or path up somewhere)
'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 "showing the way up" , "What mountaineer does" , "Use hands and feet to rise" , "Go higher up" , "Rise, mount" .)