Allowance for a knockout (9)
I believe the answer is:
provision
'allowance' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'for a knockout' is the wordplay.
'for' becomes 'pro' (as in being 'pro' something).
'a knockout' becomes 'vision' (I can't justify this - if you can you should believe this answer much more).
'pro'+'vision'='PROVISION'
Can you help me to learn more?
(Other definitions for provision that I've seen before include "Catering" , "facilities" , "prior measures made" , "Something supplied" , "Supply; condition" .)