Heaps of accidents (6)
I believe the answer is:
stacks
This could be a double definition.
'heaps' is the first definition.
('stack' can be a synonym of 'heap')
'accidents' is the second definition.
Although both the answer and definition are plural nouns, I can't see how one could define the other.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for stacks that I've seen before include "Large tall chimneys" , "bags?" , "Orderly heaps as of hay" , "Orderly piles or heaps" , "Ricks" .)