A banned substance coating man and ape, this defoliant (5,6)
I believe the answer is:
agent orange
'this defoliant' is the definition.
(I've seen this before)
'a banned substance coating man and ape' is the wordplay.
I cannot really see how this works, but
'a' could be 'an' and 'an' is located in the answer.
'substance' could be 'ge' (Ge is an example) and 'ge' is found within the answer.
'man' could be 'r' (abbreviation for rook, a chess piece or 'man') and 'r' is found in the answer.
'and' could be 'n' (common abbreviation for 'and') and 'n' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for agent orange that I've seen before include "This takes leaves off" , "Controversial weapon" , "destructive chemical" , "Poisonous chemical" , "What defoliates" .)