Something missing in favourite feature of skirt (7)
I believe the answer is:
placket
'feature of skirt' is the definition.
(type of cut in a garment)
'something missing in favourite' is the wordplay.
'something missing' becomes 'lack' (something wanting or lacking).
'in' indicates putting letters inside.
'favourite' becomes 'pet' (synonyms).
'lack' put into 'pet' is 'PLACKET'.
(Other definitions for placket that I've seen before include "opening" , "Piece of cloth" .)