Invest and invest, investing reserve (5-2)

I believe the answer is:

stand-in

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'investing reserve' is the definition.
The answer and definition can be both to do with ownership as well as being verbs in their base form.
Perhaps you can see a link between them that I don't see?

'invest and invest' is the wordplay.
'STAND IN' is hidden within the letters.
However, I am uncertain how this is indicated.

Can you help me to learn more?

(Another definition for stand-in that I've seen is " Substitute".)

I've seen this clue in The Guardian.

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