Semi-slave, endlessly cheeky revolutionary (4)
I believe the answer is:
serf
'semi-slave' is the definition.
(feudal worker)
'endlessly cheeky revolutionary' is the wordplay.
'endlessly' means to remove the last letter.
'cheeky' becomes 'fresh' (I've seen this before).
'revolutionary' is a reversal indicator.
'fresh' with its last letter taken off is 'fres'.
'fres' backwards is 'SERF'.
(Other definitions for serf that I've seen before include "Tied estate worker" , "Bondman" , "Labourer bound" , "Medieval villein" , "Old worker" .)