Fiancé exhibits such intense stress (5,6)

I believe the answer is:

acute accent

'fiance exhibits such' is the definition.
('fianc' has an acute accent over the E)

'intense stress' is the wordplay.
'intense' becomes 'acute' (synonyms).
'stress' becomes 'accent' (accent can mean to emphasise or stress).
'acute'+'accent'='ACUTE ACCENT'

(Another definition for acute accent that I've seen is " This vowel adjustment".)

I've seen this clue in The Guardian.

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