Major work getting OUP excited, investing in lots of champagne (6,4)
I believe the answer is:
magnum opus
'major work' is the definition.
'magnum opus' can be an answer for 'work' (I have seen 'Great work ' mean 'magnum opus' so perhaps 'work' could also mean 'magnum opus'). I'm unsure of the 'major' bit.
'oup excited investing in lots of champagne' is the wordplay.
'excited' indicates anagramming the letters.
'investing in' indicates putting letters inside.
'lots of champagne' becomes 'magnums' (I can't explain this - if you can you should give a lot more credence to this answer).
'oup' is an anagram of 'opu'.
'opu' put inside 'magnums' is 'MAGNUM OPUS'.
'getting' is the link.
Can you help me to learn more?
(Other definitions for magnum opus that I've seen before include "Masterpiece" , "major achievement" , "Greatest work of an artist" , "great achievement" , "finest creation" .)