Contentious young woman making first appearance on American board (9)
I believe the answer is:
debatable
'contentious' is the definition.
(both can mean controversial)
'young woman making first appearance on american board' is the wordplay.
'young woman making first appearance' becomes 'deb' (short for debutante).
'on' says to put letters next to each other.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'board' becomes 'table' (both can mean food).
'deb'+'a'+'table'='DEBATABLE'
(Other definitions for debatable that I've seen before include "subject to discussion" , "Moot" , "Open to argument" , "Open to question" , "Dubious" .)