Skivvy (6)
I believe the answer is:
drudge
'skivvy' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for drudge that I've seen before include "skivvy" , "Menial labourer" , "Menial servant" , "One does long and boring work" , "One who does monotonous work" .)