He pettily criticises government line in African state (7)
I believe the answer is:
niggler
'he pettily criticises' is the definition.
(to niggle is to criticise or complain)
'government line in african state' is the wordplay.
'government' becomes 'g' (abbreviation for government).
'line' becomes 'l' (used when specifying particular lines from a poem).
'in' means one lot of letters goes inside another.
'african state' becomes 'niger' (country in Africa).
'g'+'l'='gl'
'gl' put inside 'niger' is 'NIGGLER'.
(Another definition for niggler that I've seen is " Nit-picker".)