A profit doubled? (5)

I believe the answer is:

again

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'a profit doubled?' is the definition.
I can't judge whether this defines the answer.

'a profit' is the wordplay.
'profit' becomes 'gain' (synonyms).
'a'+'gain'='AGAIN'

Can you help me to learn more?

(Other definitions for again that I've seen before include "repeat order" , "Ocne more" , "Furthermore" , "Next time" , "second term" .)

I've seen this clue in the Evening Standard.

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