Gradual increase in one Arctic broadcast (9)

I believe the answer is:

accretion

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'gradual increase' is the definition.
'accretion' can be an answer for 'increase' (accretion is a kind of increase). I'm not sure about the 'gradual' bit.

'one arctic broadcast' is the wordplay.
'broadcast' indicates an anagram (letters scattered or cast around).
'one'+'arctic'='onearctic'
'onearctic' is an anagram of 'ACCRETION'.

'in' acts as a link.

Can you help me to learn more?

(Other definitions for accretion that I've seen before include "extra part" , "Something added" , "Extra amount" , "Gradual growth, increase" .)

I've seen this clue in The Daily Express.

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