Impound weapon to catch single villain in Gotham City (7)
I believe the answer is:
penguin
'villain in gotham city' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'impound weapon to catch single' is the wordplay.
'impound' becomes 'pen' (I can't justify this - if you can you should give a lot more credence to this answer).
'weapon' becomes 'gun' (gun is a kind of weapon).
'to catch' means one lot of letters goes inside another.
'single' becomes 'I' (one).
'gun' placed around 'i' is 'guin'.
'pen'+'guin'='PENGUIN'
Can you help me to learn more?
(Other definitions for penguin that I've seen before include "Waddling bird" , "Flightless marine bird" , "Swimming bird" , "Black-and-white Arctic bird" , "King's an example" .)