Top of bill, moi! (4)
I believe the answer is:
Here is my best explanation:
'top' is the definition.
('acme' can be a synonym of 'top')
'bill moi' is the subsidiary indication.
'bill' becomes 'ac'.
'moi' becomes 'me' (French, and used for comic effect in English).
'of' is the link.
(Other definitions for acme that I've seen before include "summit?", "Summit of achievement", "High point of excellence", "crisis in history", "crown", "Height of achievement", "Summit - maximum", "Zenith - optimum", "Highest point (of something)" and "Summit - climax".)