Indicator of sarcasm is terrible to a squire (3,6)

I believe the answer is:

air quotes

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'indicator of sarcasm' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'terrible to a squire' is the wordplay.
'terrible' is an anagram indicator.
'to'+'a'+'squire'='toasquire'
'toasquire' is an anagram of 'AIR QUOTES'.

'is' is the link.

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I've seen this clue in The Times.

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