Indigenous American's trousers not quite acceptable (7)
I believe the answer is:
chinook
'indigenous american's' is the definition.
(the Chinook are a Native American people)
'trousers not quite acceptable' is the wordplay.
'trousers' becomes 'chinos' (chinos are a type of trousers).
'not quite' means to remove the last letter.
'acceptable' becomes 'OK' (OK can mean acceptable or fine).
'chinos' with its final letter taken away is 'chino'.
'chino'+'ok'='CHINOOK'
(Other definitions for chinook that I've seen before include "What blows" , "North American wind, native or language" , "Arctic wind" , "nickname of US State" , "warm one" .)