Notice alpha male is first man (4)
I believe the answer is:
adam
'first man' is the definition.
(first man in the Bible)
'notice alpha male' is the wordplay.
'notice' becomes 'ad' (short for advert).
'alpha' becomes 'a' (phonetic alphabet: alpha, bravo, charlie etc.).
'male' becomes 'm' (common abbreviation).
'ad'+'a'+'m'='ADAM'
'is' is the link.
(Other definitions for adam that I've seen before include "First man in the Bible" , "first in the race?" , "Biblical first human" , "who was tempted by mate?" , "one might confuse with total stranger" .)