Girl’s pannier missing outside (5)
I believe the answer is:
annie
'girl's' is the definition.
'pannier missing outside' is the wordplay.
'missing outside' indicates the central letters.
The middle letters of 'pannier' are 'ANNIE'.
(Other definitions for annie that I've seen before include "Musical about red-handed Orphan girl" , "Sharpshooter Oakley or musical orphan" , "Musical heroine" , "Popular stage musical" , "1977 Broadway musical" .)