Meeting's leader wearing superb top (4)
I believe the answer is:
acme
'top' is the definition.
('acme' can be a synonym of 'top')
'meeting's leader wearing superb' is the wordplay.
'leader' says to take the initial letters.
'wearing' is an insertion indicator.
'superb' becomes 'ace' (I've seen this in other clues).
The first letter of 'meetings' is 'm'.
'm' placed within 'ace' is 'ACME'.
(Other definitions for acme that I've seen before include "Pinnacle" , "crisis in history" , "Height of excellence" , "Peak of perfection" , "Top or highest point" .)