Drilling for rounds in obscure packaging (12)
I believe the answer is:
shadowboxing
'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" .)