Mark, foreign, has an appealing inflection (5,6)

I believe the answer is:

acute accent

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'mark' is the definition.
(acute accent is a kind of mark)

'an appealing inflection' is the wordplay.
'an' becomes 'a'.
'appealing' becomes 'cute' (I've seen this in another clue).
'inflection' becomes 'accent' (accent is a kind of inflection).
'a'+'cute'+'accent'='ACUTE ACCENT'

'foreign has' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.

Can you help me to learn more?

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

I've seen this clue in The Daily Express.

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