Member within is showing wicked things (4)
I believe the answer is:
imps
'wicked things' is the definition.
(imps are evil creatures)
'member within is' is the wordplay.
'member' becomes 'MP' (Member of Parliament).
'within' is an insertion indicator.
'mp' put within 'is' is 'IMPS'.
'showing' is the link.
(Other definitions for imps that I've seen before include "Mischievous fairies" , "Little monkeys?" , "Mischievous characters" , "Naughty sprites" , "Little devils or scamps" .)