They’re pretty worthless, not having been new for years (5)
I believe the answer is:
pence
'years' is the definition.
Although both the answer and definition are plural nouns, I don't understand how one could define the other.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for pence that I've seen before include "Money used to be pounds, shillings and ....." , "Lowest denomination of British currency" , "offering to St Peter" , "Small change" , "Small coins" .)