Contents of box for designer footwear (6)
I believe the answer is:
oxford
'footwear' is the definition.
(oxford is a kind of footwear)
'contents of box for designer' is the wordplay.
'contents of' says the answer is hidden in the clue.
'OXFORD' is hidden within 'box for designer'.
(Other definitions for oxford that I've seen before include "Dark blue university?" , "British university town" , "Boat Race's Dark Blues" , "Isis their second boat" , "River in Newcastle" .)