Maximise efforts to serve a mug each (2,3,3,3)
I believe the answer is:
do all one can
'maximise efforts' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'serve a mug each' is the wordplay.
I cannot quite understand how this works, but
'serve' could be 'do' ('do' can be a synonym of 'serve') and 'do' is found within the answer.
'a' could be 'one' and 'one' is found in the answer.
'mug' could be 'can' and 'can' is found in the answer.
'each' could be 'all' ('all' can be similar in meaning to 'each') and 'all' is present in the answer.
No letters remain.
This explanation may well be incorrect...
'to' is the link.
Can you help me to learn more?
(Another definition for do all one can that I've seen is " Try one's hardest".)