Sirens upsetting to horse (7)

I believe the answer is:

hooters

'sirens' is the definition.
(sirens hoot or make a sound)

'upsetting to horse' is the wordplay.
'upsetting' is an anagram indicator.
'to'+'horse'='tohorse'
'tohorse' anagrammed gives 'HOOTERS'.

(Another definition for hooters that I've seen is " Sirens; horns".)

I've seen this clue in The Telegraph.

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