She, a GI, upset hostess (6)
I believe the answer is:
geisha
'hostess' is the definition.
(Japanese woman hosting or entertaining men)
'she a gi upset' is the wordplay.
'upset' is an anagram indicator.
'she'+'a'+'gi'='sheagi'
'sheagi' with letters rearranged gives 'GEISHA'.
(Other definitions for geisha that I've seen before include "Professional female companion in Japan" , "Japanese woman trained to please men" , "Japanese girl trained to entertain men" , "Japanese paid companion" , "Hostess in a kimono" .)