Wet politician in power (6)
I believe the answer is:
swampy
'wet' is the definition.
('swampy' can be similar in meaning to 'wet')
'politician in power' is the wordplay.
'politician' becomes 'mp'.
'in' means one lot of letters goes inside another.
'power' becomes 'sway' (sway is a kind of power**).
'mp' placed inside 'sway' is 'SWAMPY'.
(Other definitions for swampy that I've seen before include "uncultivated and wet" , "Boggy, marshy" , "Bog-like" , "Boggy -waterlogged" , "gets bogged down?" .)