Fish with a notion (4)

I believe the answer is:

idea

'notion' is the definition.
(both can mean a thought)

'fish with a' is the wordplay.
'fish' becomes 'ide' (type of fish).
'with' means one lot of letters go next to another.
'ide'+'a'='IDEA'

(Other definitions for idea that I've seen before include "Aim" , "Suggestion" , "Flash of inspiration?" , "A suspicion of" , "Sudden inspiration?" .)

I've seen this clue in the Sydney Morning Herald and The Telegraph.

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