Joker gets better around end of performances (7)
I believe the answer is:
punster
'joker' is the definition.
(someone who makes puns)
'better around end of performances' is the wordplay.
'better' becomes 'punter' (synonyms).
'around' means one lot of letters goes inside another.
'end of performances' becomes 's' (I can't justify this - if you can you should give a lot more credence to this answer).
'punter' enclosing 's' is 'PUNSTER'.
'gets' acts as a link.
(Other definitions for punster that I've seen before include "Comedian" , "Verbal joker" , "user of wordplay" , "One makes jokes" , "One who plays on words" .)