Relationship just beyond alpha female (6)
I believe the answer is:
affair
'relationship' is the definition.
(I know that affair is a type of sexual relationship)
'just beyond alpha female' is the wordplay.
'just' becomes 'fair' (just can mean fair in the sense of showing justice).
'beyond' says to put letters next to each other.
'alpha' becomes 'a' (phonetic alphabet: alpha, bravo, charlie etc.).
'female' becomes 'f' (common abbreviation).
'a'+'f'='af'
'fair' put after 'af' is 'AFFAIR'.
(Other definitions for affair that I've seen before include "Involvement" , "Romantic relationship between two unmarried people" , "Concern -- extramarital relationship" , "River dam" , "A function or a romance" .)