Upside-down cakes perhaps on edge (8)
I believe the answer is:
stressed
'on edge' is the definition.
(I've seen this before)
'upside-down cakes perhaps' is the wordplay.
'upside down' shows that the letters should be reversed in order.
'cakes perhaps' becomes 'desserts' (cakes are a type of dessert).
'desserts' reversed gives 'STRESSED'.
(Other definitions for stressed that I've seen before include "overwrought" , "Harassed, strained" , "Emphasised, underlined" , "anxious" , "Drew attention to" .)