Carp saw other banks (5)
I believe the answer is:
motor
'carp' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'saw other banks' is the wordplay.
'saw' becomes 'mot' (I am not sure about this - if you are sure you should believe this answer much more).
'banks' suggests removing the centre (the sides or banks of the word).
'other' with its centre removed is 'or'.
'mot'+'or'='MOTOR'
Can you help me to learn more?
(Other definitions for motor that I've seen before include "Engine of vehicle" , "Wheels" , "Driver" , "Car (colloq,)" , "Car; powered machine" .)