Piles of old cars? (5)
I believe the answer is:
heaps
This might be a double definition.
'piles' is the first definition.
('heap' can be a synonym of 'pile')
'old cars?' is the second definition.
'heaps' can be an answer for 'cars?' (heap is a kind of car). I am unsure of the 'old' bit.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for heaps that I've seen before include "Lots (of piles?)" , "Shape (anag) - lots" , "Mounds; lots" , "Mounds, stacks" , "A large number; untidy mounds" .)