Is smoking it hard work? (3)
I believe the answer is:
fag
'work?' is the definition.
(fagging is a kind of working)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for fag that I've seen before include "Hard work - cigarette (slang)" , "Tiring task; cigarette" , "He'll do anything you ask" , "Tedious chore" , "an awful bore!" .)