Government leader to prepare member of the clergy (5,8)
I believe the answer is:
prime minister
'government leader' is the definition.
(leader of the government in many countries)
'prepare member of the clergy' is the wordplay.
'prepare' becomes 'prime' (to prime is to prepare or make ready).
'member of the clergy' becomes 'minister' (a church minister).
'prime'+'minister'='PRIME MINISTER'
'to' acts as a link.
(Other definitions for prime minister that I've seen before include "Head of government" , "Senior political post" , "Law once in UK" , "political leader" , "Head of state" .)