Knock down a casual boyfriend (5)
I believe the answer is:
fella
'casual boyfriend' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'knock down a' is the wordplay.
'knock down' becomes 'fell' (I've seen this before).
'fell'+'a'='FELLA'
Can you help me to learn more?
(Other definitions for fella that I've seen before include "Bloke" , "Chap" , "Guy" .)