Fashionable container sinking and glowing (12)
I believe the answer is:
incandescent
'glowing' is the definition.
(I've seen this before)
'fashionable container sinking' is the wordplay.
'fashionable' becomes 'in' ('in' can be similar in meaning to 'fashionable').
'container' becomes 'can' (can is a kind of container**).
'sinking' becomes 'descent'.
'in'+'can'+'descent'='INCANDESCENT'
'and' is the link.
(Other definitions for incandescent that I've seen before include "White-hot" , "extremely angry" , "Mad" , "Glowing with heat" , "Dazzling" .)