Drink beginning to excite religious leader (4)
I believe the answer is:
pope
'religious leader' is the definition.
(I've seen this in another clue)
'drink beginning to excite' is the wordplay.
'drink' becomes 'pop' (fizzy pop).
'beginning to' says to take the initial letters.
The initial letter of 'excite' is 'e'.
'pop'+'e'='POPE'
(Other definitions for pope that I've seen before include "Head of Roman Catholic Church" , "Top bishop" , "Francis < Alexander" , "English poet, d. 1744" , "Satirist" .)