Starts on the straight approach — right for leader (4)
I believe the answer is:
'leader' is the definition.
(I've seen this before)
'starts on the straight approach right' is the wordplay.
'starts on' says to take the initial letters.
The first letters of 'the straight approach right' is 'TSAR'.
'for' acts as a link.
(Other definitions for tsar that I've seen before include "Title given to the kings of Bulgaria" , "Absolute ruler" , "Old Russian 22" , "A former Russian ruler - rats to him" , "Star for a Russian emperor" .)