Contemptible male in love with American (7)
I believe the answer is:
heinous
'contemptible' is the definition.
(thesaurus)
'male in love with american' is the wordplay.
'male' becomes 'he' (he refers to a man).
'love' becomes 'o' (love means zero in tennis).
'with' is a charade indicator (letters next to each other).
'american' becomes 'us' (abbreviation for United States).
'he'+'in'+'o'+'us'='HEINOUS'
(Other definitions for heinous that I've seen before include "Hateful" , "Loathsome" , "Utterly odious (crime)" , "Very wicked, maybe in-house" , "Diabolic" .)