Exhibit concern for the world of entertainment (4,8)
I believe the answer is:
show business
'the world of entertainment' is the definition.
(I've seen this before)
'exhibit concern' is the wordplay.
'exhibit' becomes 'show' ('show' can be a synonym of 'exhibit').
'concern' becomes 'business' (business is a kind of concern**).
'show'+'business'='SHOW-BUSINESS'
'for' acts as a link.
(Other definitions for show business that I've seen before include "Entertainment industry" , "Theatre/music industry" , "The world of entertainment" .)