Paper cash exchanged for pile of junk (5,4)
I believe the answer is:
scrap heap
'pile of junk' is the definition.
'scrap heap' can be an answer for 'pile' (I have seen 'Pile of rubbish' mean 'scrap heap' so perhaps 'pile' could also mean 'scrap heap'). I'm not sure about the 'of junk' bit.
'paper cash exchanged' is the wordplay.
'exchanged' indicates an anagram.
'paper'+'cash'='papercash'
'papercash' anagrammed gives 'SCRAP-HEAP'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for scrap heap that I've seen before include "Pile of rubbish" , "Tip" , "Discard pile" , "Pile of discarded metal" , "Waste" .)