More than one mischief-maker is ringing politician (4)
I believe the answer is:
imps
'more than one mischief-maker' is the definition.
'is ringing politician' is the wordplay.
'ringing' means one lot of letters goes inside another.
'politician' becomes 'mp'.
'is' enclosing 'mp' is 'IMPS'.
(Other definitions for imps that I've seen before include "Mischievous characters" , "Mischievous sprites" , "repairs (for a wing)" , "Small devils or mischievous children" , "Children causing trouble" .)