Current member, one making mischief (3)
I believe the answer is:
imp
'one making mischief' is the definition.
(imps are mischievous creatures)
'current member' is the wordplay.
'current' becomes 'I' (symbol for electric current).
'member' becomes 'MP' (Member of Parliament).
'i'+'mp'='IMP'
(Other definitions for imp that I've seen before include "Small devil or sprite" , "Mischievous fairy No.1" , "one likely to cause trouble" , "Scamp" , "Naughty child" .)