Pound lump of tobacco (4)
I believe the answer is:
quid
This clue could be a double definition.
'pound lump' is the first definition.
'quid' can be an answer for 'pound' (UK slang for a pound). I am not sure about the 'lump' bit.
'tobacco' is the second definition.
(I've seen this before)
'of' is the link.
Can you help me to learn more?
(Other definitions for quid that I've seen before include "1 GBP - piece of chewing tobacco" , "that's chewed" , "One fifth of a fiver" , "Pound (colloq.)" , "Pound (informal)" .)