Killer fish, nasty type (9)

I believe the answer is:

garrotter

'killer' is the definition.
(garrotter is a kind of killer)

'fish nasty type' is the wordplay.
'fish' becomes 'gar' (gar is a kind of fish).
'nasty type' becomes 'rotter' (informal term for a nasty person).
'gar'+'rotter'='GARROTTER'

(Other definitions for garrotter that I've seen before include "Executioner" , "Killer" .)

I've seen this clue in The Guardian.

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