Head of government certainly not welcomed by African country, a bloomer (8)
I believe the answer is:
magnolia
'bloomer' is the definition.
(a magnolia might be in bloom)
'head of government certainly not welcomed by african country a' is the wordplay.
'head of government' becomes 'g' (I am not sure about this - if you are sure you should believe this answer much more).
'certainly not' becomes 'no'.
'welcomed by' indicates putting letters inside (letters welcomed inside).
'african country' becomes 'mali' (country in Africa).
'g'+'no'='gno'
'gno' going inside 'mali' is 'magnoli'.
'magnoli'+'a'='MAGNOLIA'
(Other definitions for magnolia that I've seen before include "Fragrant bloom and popular paint colour" , "Main gaol (anag)" , "ornamental tree" , "Tree with creamy-white flowers" , "bush" .)