A pound almost left, and five US cents (6)
I believe the answer is:
nickel
'five us cents' is the definition.
(I've seen this before)
'a pound almost left' is the wordplay.
'a pound' becomes 'nicker' (I've seen this before).
'almost' means to remove the last letter (most of the word but not all of it).
'left' becomes 'l' (common abbreviation).
'nicker' with its last letter taken off is 'nicke'.
'nicke'+'l'='NICKEL'
'and' acts as a link.
(Other definitions for nickel that I've seen before include "Metal; five US cents" , "Metal - 5 cents" , "US 5 cents" , "Atomic number 28" , "US five cent piece" .)