Duck revolutionary leader (7)
I believe the answer is:
redhead
'duck' is the definition.
(redhead is a kind of duck)
'revolutionary leader' is the wordplay.
'revolutionary' becomes 'red' (red can informally mean communist).
'leader' becomes 'head' (head is a kind of leader).
'red'+'head'='REDHEAD'
(Other definitions for redhead that I've seen before include "'Carrot top'" , "Ginger-haired person" , "One with auburn hair" , "Person with rufous hair" , "Fergie perhaps" .)