Frowned when a bovine utterance disturbed the deer (7)

I believe the answer is:

lowered

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'frowned' is the definition.
('lower' can be a synonym of 'frown')

'a bovine utterance disturbed the deer' is the wordplay.
'a bovine utterance' becomes 'low' (I can't explain this - if you can you should believe this answer much more).
'disturbed' indicates an anagram (the order of letters is disturbed).
'deer' is an anagram of 'ered'.
'low'+'ered'='LOWERED'

'when' is the link.

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(Other definitions for lowered that I've seen before include "Let down gently" , "Brought down" , "looked sullen" , "Moved something down" , "Threatened" .)

I've seen this clue in the Evening Standard.

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