Feline figure seen within banks of lagoon (4)
I believe the answer is:
lion
'feline' is the definition.
(I know that Lion is a type of big cat)
'figure seen within banks of lagoon' is the wordplay.
'figure' becomes 'io' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'seen within' means one lot of letters goes inside another.
'banks of' means to remove the middle letters (the banks are the sides of the word).
'lagoon' with its middle taken out is 'ln'.
'io' inserted within 'ln' is 'LION'.
Can you help me to learn more?
(Other definitions for lion that I've seen before include "cowardly character in Oz" , "one showing unusual courage?" , "Cat, the king of the beasts" , "Animal which Judah is described as" , "King of the jungle" .)