Partygoer's second name (4)

I believe the answer is:

stag

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'partygoer's' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.

'second name' is the wordplay.
'second' becomes 's' (common abbreviation).
'name' becomes 'tag' (tag can mean a name or label).
's'+'tag'='STAG'

Can you help me to learn more?

(Other definitions for stag that I've seen before include "Male deer; speculator" , "involving men" , "Investor" , "Stock market speculator" , "Stock Exchange speculator standing" .)

I've seen this clue in The Independent.

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