Make old boy fib about leader of government (6)
I believe the answer is:
oblige
'make' is the definition.
(I know that oblige is a type of make)
'old boy fib about leader of government' is the wordplay.
'old boy' becomes 'OB' (abbreviation for a private school 'old boy').
'fib' becomes 'lie' (I've seen this in another clue).
'about' is an insertion indicator.
'leader of' indicates taking the first letters.
The first letter of 'government' is 'g'.
'lie' enclosing 'g' is 'lige'.
'ob'+'lige'='OBLIGE'
(Other definitions for oblige that I've seen before include "Do favour or coerce" , "Hold in debt" , "Compel (someone to do something)" , "Do something as a favour to (someone)" , "serve" .)