Fashionable remnants are destroyed (2,5)
I believe the answer is:
in ruins
'are destroyed' is the definition.
(I've seen this in another clue)
'fashionable remnants' is the wordplay.
'fashionable' becomes 'in' (in can mean fashionable or trendy).
'remnants' becomes 'ruins' (I am not sure about this - if you are sure you should believe this answer much more).
'in'+'ruins'='IN RUINS'
Can you help me to learn more?
(Other definitions for in ruins that I've seen before include "Ramshackle" , "falling apart" , "Effectively destroyed" , "Broken-down" , "Wrecked" .)