Island politician a little devil (3)
I believe the answer is:
imp
'a little devil' is the definition.
(an imp is a little demon)
'island politician' is the wordplay.
'island' becomes 'i' (geographical abbreviation).
'politician' becomes 'MP' (Member of Parliament).
'i'+'mp'='IMP'
(Other definitions for imp that I've seen before include "one likely to cause trouble" , "Mischievous child" , "puck" , "Little mischief-maker" , "pickle" .)