Having piled all the wood outside, slump on the ground (8)
I believe the answer is:
collapse
'slump on the ground' is the definition.
'collapse' can be an answer for 'slump' (I've seen this before). I am unsure of the 'on the ground' bit.
'having piled all the wood outside' is the wordplay.
I cannot really understand how this works, but
an anagram of 'all' is 'lla' which is present in the answer.
'wood' could be 'copse' (a copse is a small wood) and 'copse' is present in the remaining letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for collapse that I've seen before include "Faint and fall" , "Abrupt failure of function" , "Founder" , "Break down - fall" , "Disintegration" .)