Questions politician involved in unpleasant matter (5)
I believe the answer is:
pumps
'questions' is the definition.
(as in to pump someone for information)
'politician involved in unpleasant matter' is the wordplay.
'politician' becomes 'MP' (Member of Parliament).
'involved in' is an insertion indicator.
'unpleasant matter' becomes 'pus' (I've seen this before).
'mp' placed inside 'pus' is 'PUMPS'.
(Other definitions for pumps that I've seen before include "footwear" , "Light dancing shoes - force air into" , "leading questions" , "Mechanical devices that move fluid or gas" , "Cycle attachments" .)