A pile of old wheels? (4)
I believe the answer is:
heap
This might be a double definition.
'a pile' is the first definition.
(I know that pile can be written as heap)
'old wheels?' is the second definition.
'heap' can be an answer for 'wheels?' (thesaurus). I'm not sure about the 'old' bit.
'of' is the link.
Can you help me to learn more?
(Other definitions for heap that I've seen before include "Mound, stack" , "Amass" , "Pile (of scrap?)" , "Mound; old car" , "Mound, pile" .)