A pint served up for eastern leader (4)
I believe the answer is:
raja
'eastern leader' is the definition.
(I've seen this before)
'a pint served up' is the wordplay.
'pint' becomes 'jar' (I've seen this in other clues).
'served up' shows that the letters should be reversed in order (in a down clue, going upwards).
'a'+'jar'='ajar'
'ajar' written backwards gives 'RAJA'.
'for' is the link.
(Other definitions for raja that I've seen before include "Indian prince or king" , "sovereign" , "High Indian position" , "Eastern leader" , "Prominent Indian" .)