Money-making plant? (4)

I believe the answer is:

mint

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'plant?' is the definition.
(I know that mint is a type of herb)

'money-making' is the wordplay.
'money' becomes 'm' (abbreviation used in economics).
'making' becomes 'int' (I can't justify this - if you can you should give a lot more credence to this answer).
'm'+'int'='MINT'

Can you help me to learn more?

(Other definitions for mint that I've seen before include "Vast sum of money" , "Aromatic plant; as new" , "Forge" , "Plant - in perfect condition" , "and 18 Down: Southern US cocktail" .)

I've seen this clue in The Irish Independent.

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