Head of government also greeting spiritual leader (6)
I believe the answer is:
gandhi
'spiritual leader' is the definition.
(Gandhi is an example)
'head of government also greeting' is the wordplay.
'head of' indicates taking the first letters.
'also' becomes 'and' (I've seen this before).
'greeting' becomes 'hi' (hi is a kind of greeting).
The initial letter of 'government' is 'g'.
'g'+'and'+'hi'='GANDHI'
(Other definitions for gandhi that I've seen before include "Leader who preached non-violence" , "Pacifist Indian leader" , "Indian spinner" , "Indian man of peace" , "civil rights leader" .)