The ultimate in sporting entertainment (5)
I believe the answer is:
final
'the ultimate' is the definition.
(I've seen this before)
'in sporting entertainment' is the wordplay.
'sporting' indicates putting letters inside (inserted letters wear or 'sport' others).
'entertainment' becomes 'fal' (I can't justify this - if you can you should believe this answer much more).
'in' put within 'fal' is 'FINAL'.
Can you help me to learn more?
(Other definitions for final that I've seen before include "binding" , "Not to be altered" , "Like one's journey to cemetery" , "big match" , "Conclusive" .)