Trendy bearing case (8)
I believe the answer is:
instance
'case' is the definition.
(I know that case can be written as instance)
'trendy bearing' is the wordplay.
'trendy' becomes 'in' ('in' can mean fashionable).
'bearing' becomes 'stance' (I've seen this before).
'in'+'stance'='INSTANCE'
(Other definitions for instance that I've seen before include "Canniest (anag) - occurrence" , "'Example, illustration (8)'" , "Cite as an example" , "An insect (anag.)" , "Case or example from ancients" .)