Important to welcome leader in Nigeria, an African (6)
I believe the answer is:
kenyan
'african' is the definition.
(Kenyan is an example)
'important to welcome leader in nigeria an' is the wordplay.
'important' becomes 'key' ('key' can be similar in meaning to 'important').
'to welcome' indicates putting letters inside (in sense of 'inviting in').
'leader in' says to take the initial letters.
The initial letter of 'nigeria' is 'n'.
'key' going around 'n' is 'keny'.
'keny'+'an'='KENYAN'
(Other definitions for kenyan that I've seen before include "Nationality of citizen of Nairobi" , "Eg, native of Nairobi" , "person in Africa" , "One from Nairobi" , "Native of Nairobi, say" .)