Idiot put fish with pork pie! (7)
I believe the answer is:
charlie
'idiot put' is the definition.
The definition suggests a singular noun which matches the answer.
'fish with pork pie' is the wordplay.
'fish' becomes 'char' (char is a kind of fish).
'with' is a charade indicator (letters next to each other).
'pork pie' becomes 'lie' (I've seen this in other clues).
'char'+'lie'='CHARLIE'
Can you help me to learn more?
(Other definitions for charlie that I've seen before include "Fool; C (radio comms)" , "tail-ender" , "Code word < for silly fellow" , "Comms code C" , "Silly person" .)