Extremely disappointed, as a fish might be? (6)

I believe the answer is:

gutted

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'extremely disappointed' is the definition.
(I've seen this before)

I don't understand the rest of the clue.

(Other definitions for gutted that I've seen before include "Disembowelled or destroyed by fire" , "Disappointed (sl.)" , "how fish is prepared" , "Removed the insides, of a fish perhaps" , "Destroyed internally, as building by fire" .)

I've seen this clue in The Telegraph.

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