That woman supporting American court official (5)
I believe the answer is:
usher
'court official' is the definition.
(official in a law court)
'that woman supporting american' is the wordplay.
'that woman' becomes 'her' (her refers to a woman).
'supporting' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'american' becomes 'us' (abbreviation for United States).
'her' put after 'us' is 'USHER'.
(Other definitions for usher that I've seen before include "Cinema or wedding attendant" , "Court or parliamentary official" , "One who shows people to seats" , "One conducts people to seats" , "Theatre/cinema worker" .)