An increase once more (5)

I believe the answer is:

again

'once more' is the definition.
(synonyms)

'an increase' is the wordplay.
'an' becomes 'a'.
'increase' becomes 'gain' (gaining is a kind of increasing).
'a'+'gain'='AGAIN'

(Other definitions for again that I've seen before include "10 10 [AGAIN" , "Furthermore" , "repeat order" , "Not for the first time" , "One more time, encore" .)

I've seen this clue in The Sun.

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