Leader to drink more, sadly (7)
I believe the answer is:
supremo
'leader' is the definition.
(I've seen this before)
'drink more sadly' is the wordplay.
'drink' becomes 'sup' (to sup is to drink).
'sadly' indicates anagramming the letters.
'more' anagrammed gives 'remo'.
'sup'+'remo'='SUPREMO'
'to' acts as a link.
(Other definitions for supremo that I've seen before include "Person in overall charge, really the top man" , "Top commander" , "Person invested with great authority" , "Big fish" , "top boss" .)