A politician in office, wet (6)
I believe the answer is:
dampen
'wet' is the definition.
(dampening is a kind of wetting)
'a politician in office' is the wordplay.
'politician' becomes 'mp'.
'in' means one lot of letters goes inside another.
'office' becomes 'den' (I've seen this before).
'a'+'mp'='amp'
'amp' placed inside 'den' is 'DAMPEN'.
(Other definitions for dampen that I've seen before include "Stifle" , "Moisten" , "Make moist or depress spirits" , "get a bit wet" , "Discourage in moist manner" .)