Small pistol socialist turned on lookalike (9)
I believe the answer is:
derringer
'small pistol' is the definition.
(I've seen this before)
'socialist turned on lookalike' is the wordplay.
'socialist' becomes 'red' (red is a kind of socialist**).
'turned' is a reversal indicator.
'on' means one lot of letters go next to another.
'lookalike' becomes 'ringer' (I've seen this before).
'red' backwards is 'der'.
'der'+'ringer'='DERRINGER'
(Other definitions for derringer that I've seen before include "Small pistol used by gamblers in western films" , "Short-barrelled American pistol" , "Pocket pistol" , "Weapon" .)