A pound of tobacco? (4)
I believe the answer is:
quid
I believe this clue is a double definition.
'a pound' is the first definition.
('quid' can be a synonym of 'pound')
'tobacco?' is the second definition.
(I've seen this before)
'of' acts as a link.
(Other definitions for quid that I've seen before include "that's chewed" , "One fifth of a fiver" , "plug?" , "Pound sterling (slang)" , "One pound sterling" .)