Dresses delivered boring look, sent back (7)
I believe the answer is:
enrobes
'dresses' is the definition.
(I've seen this in another clue)
'delivered boring look sent back' is the wordplay.
'delivered' becomes 'born' (as in a baby being delivered).
'boring' is an insertion indicator (to bore something can mean to drill into it).
'look' becomes 'see'.
'sent back' shows that the letters should be reversed in order.
'born' placed into 'see' is 'seborne'.
'seborne' in reverse letter order is 'ENROBES'.
(Another definition for enrobes that I've seen is " coats".)