The cleaner was not him! (6)
I believe the answer is:
washer
'the cleaner' is the definition.
(I've seen this before)
'not him' is the wordplay.
I cannot really understand how this works, but
'him' could be 'asher' and 'asher' is found in the answer.
A single letter 'w' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
'was' is the link.
Can you help me to learn more?
(Other definitions for washer that I've seen before include "Cleaner" , "Joint-sealing ring" , "Seal preventing leakage" , "Tap seal" , "Plumber's rubber ring" .)