African male, excellent, ingests arsenic (5)
I believe the answer is:
masai
'african' is the definition.
(the Masai are an ethnic group of Kenya)
'male excellent ingests arsenic' is the wordplay.
I cannot quite understand how this works, but
'male' could be 'm' (common abbreviation) and 'm' is present in the answer.
'excellent' could be 'ai' (resembles 'A1', old-fashioned term for excellent) and 'ai' is present in the answer.
'arsenic' could be 'as' (As is the chemical symbol for arsenic) and 'as' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for masai that I've seen before include "African tribespeople" , "Price increase" , "People of the highlands of Kenya and Tanzania" , "Kenyan language" , "East African people" .)