Shady group of men stealing pounds (5)
I believe the answer is:
unlit
'shady' is the definition.
(I've seen this before)
'group of men stealing pounds' is the wordplay.
'group of men' becomes 'unit' (I can't explain this - if you can you should give a lot more credence to this answer).
'stealing' is an insertion indicator.
'pounds' becomes 'l' (abbreviation e.g. Lsd - pounds, shillings, pence).
'unit' going around 'l' is 'UNLIT'.
Can you help me to learn more?
(Other definitions for unlit that I've seen before include "Shady" , "dim" , "Not yet fired up" , "Not illuminated" , "Until (anag.)" .)