Baron associated with timeless TV corporation (5)
I believe the answer is:
'corporation' is the definition.
(corporation can humorously mean belly fat)
'baron associated with timeless tv' is the wordplay.
'baron' becomes 'b'.
'associated with timeless tv' becomes 'elly' (I can't justify this - if you can you should believe this answer much more).
(Other definitions for belly that I've seen before include "Paunch" , "Tummy" , "Stomach" , "Abdomen" , "Corporation" .)