Change mind about cross person that’s annoying (5)

I believe the answer is:

vexer

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'annoying' is the definition.
Both the answer and definition are singular nouns.
Maybe there's a link between them I don't understand?

'change mind about cross person' is the wordplay.
'change mind about' becomes 'ver' (I can't explain this - if you can you should give a lot more credence to this answer).
'cross' indicates putting letters inside.
'person' becomes 'ex' (ex is a kind of person).
'ver' enclosing 'ex' is 'VEXER'.

'that's' is the link.

Can you help me to learn more?

I've seen this clue in The Times.

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