Small bird seen by old Balkan leader (4)
I believe the answer is:
tito
'balkan leader' is the definition.
(I've seen this in another clue)
'small bird seen by old' is the wordplay.
'small bird' becomes 'tit' (I've seen this before).
'seen by' means one lot of letters go next to another.
'old' becomes 'o' (abbreviation).
'tit'+'o'='TITO'
(Other definitions for tito that I've seen before include "Josip Broz, d. 1980" , "Yugoslavian freedom fighter and president" , "Head of state" , "Yugoslav marshall, prime minister and president, d. 1980" , "Statesman once" .)