Fish caught near the harbour (7)

I believe the answer is:

haddock

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'fish' is the definition.
(I know that haddock is a type of fish)

'caught near the harbour' is the wordplay.
'caught near' becomes 'had' (I can't explain this - if you can you should believe this answer much more).
'the harbour' becomes 'dock' (I've seen this before).
'had'+'dock'='HADDOCK'

Can you help me to learn more?

(Other definitions for haddock that I've seen before include "Fish, often smoked" , "Fish similar to but smaller than cod" , "Cod-like fish" , "Fish like cod but smaller" , "Swimmer" .)

I've seen this clue in The Irish Independent.

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