Crossword Genius

Drilling for rounds in obscure packaging (12)

Ross

I believe the answer is:

shadowboxing

I'm a little stuck... Click here to teach me more about this clue!

'drilling for rounds' is the definition.
I can't tell whether this defines the answer.

'obscure packaging' is the wordplay.
'obscure' becomes 'shadow' (shadowing is a kind of obscuring).
'packaging' becomes 'boxing' ('box' can be a synonym of 'package').
'shadow'+'boxing'='SHADOWBOXING'

'in' acts as a link.

Can you help me to learn more?

(Other definitions for shadowboxing that I've seen before include "Sparring with oneself?" , "Sparring with an imaginary opponent" , "Fighting against an imaginary opponent" .)

I've seen this clue in the Sydney Morning Herald.
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