Coats designed for an opera (5)
I believe the answer is:
tosca
'an opera' is the definition.
(I've seen this before)
'coats designed' is the wordplay.
'designed' indicates an anagram (designed with the letters).
'coats' with letters rearranged gives 'TOSCA'.
'for' is the link.
(Other definitions for tosca that I've seen before include "Puccini's 2 dn heroine" , "Puccini opera set in Rome" , "role for diva" , "Leaping opera heroine" , "Ascot (anag) - operatic heroine" .)