Much champagne pours out without hint of restraint: great work! (6,4)
I believe the answer is:
magnum opus
'great work' is the definition.
(I've seen this before)
'much champagne pours out without hint of restraint' is the wordplay.
I cannot really see how this works, but
'of' could be 'o' and 'o' is located in the answer.
'much champagne' could be 'magnum' (big wine bottle) and 'magnum' is located in the answer.
The remaining letters 'pus' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for magnum opus that I've seen before include "Writer's greatest work" , "Great work" , "one's best" , "Creative feat" , "finest creation" .)