Partner felt breath becoming irregular (10)

I believe the answer is:

betterhalf

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'irregular' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'partner felt breath' is the wordplay.
'felt breath' anagrams to 'BETTERHALF'.
But, I am not sure how the anagram is indicated.

'becoming' acts as a link.

Can you help me to learn more?

I've seen this clue in The Irish Times.

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