Boy collecting ace coin? (5)

I believe the answer is:

money

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'coin?' is the definition.
(thesaurus)

'boy collecting ace' is the wordplay.
'boy' becomes 'my' (I can't explain this - if you can you should believe this answer much more).
'collecting' means one lot of letters goes inside another.
'ace' becomes 'one' (synonyms).
'my' going around 'one' is 'MONEY'.

Can you help me to learn more?

(Other definitions for money that I've seen before include "Legal tender" , "tin" , "ready" , "Lucre" , "Mazuma, ackers or dosh" .)

I've seen this clue in The Independent.

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