More than one troublemaker is nabbing MP (4)
I believe the answer is:
imps
'more than one troublemaker' is the definition.
(I've seen this before)
'is nabbing mp' is the wordplay.
'nabbing' indicates putting letters inside.
'is' placed around 'mp' is 'IMPS'.
(Other definitions for imps that I've seen before include "Cheeky little devils" , "Little monkeys?" , "Mischievous fairies" , "naughty children" , "Naughty sprites" .)