Shock when ducks upset horse (9)

I believe the answer is:

appaloosa

'horse' is the definition.
(Appaloosa is an example)

'shock when ducks upset' is the wordplay.
'shock' becomes 'appal' (synonyms).
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'ducks' becomes 'OO' (two O's - duck means zero in cricket).
'upset' says the letters should be written in reverse.
'as'+'oo'='asoo'
'asoo' backwards is 'oosa'.
'appal'+'oosa'='APPALOOSA'

(Another definition for appaloosa that I've seen is " Horse breed, with spotted rump".)

I've seen this clue in The Times.

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