Going round dressed like a priest (10)

I believe the answer is:

investment

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'going' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe they are linked in a way I don't understand?

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for investment that I've seen before include "Outlay for profit" , "Something bought for its future value" , "Thing worth buying for the future" , "Thing worth buying for expected profit" , "siege" .)

I've seen this clue in the Evening Standard.

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