What's in magnum? Not I'm thinking cheap bubbly (9)
I believe the answer is:
champagne
'bubbly' is the definition.
(I know that bubbly can be written as champagne)
'what's in magnum? not i'm thinking cheap' is the wordplay.
I cannot quite see how this works, but
'i'm' could be 'am' (I've seen this in other clues) and 'am' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for champagne that I've seen before include "French wine district" , "pop" , "The drink called bubbly" , "Sparkling wine of north-eastern France" , "Someone whose life style belies their professed radical politics" .)