Band her co-star confused (9)
I believe the answer is:
orchestra
'band' is the definition.
(musical band)
'her co-star confused' is the wordplay.
'confused' is an anagram indicator.
'her'+'co'+'star'='hercostar'
'hercostar' anagrammed gives 'ORCHESTRA'.
(Other definitions for orchestra that I've seen before include "Carthorse (anag)" , "alternative to the organ" , "Other cars (anag.)" , "players in pit" , "Gamelan, for instance" .)