Laugh with merriment, no end, after performance (6)
I believe the answer is:
giggle
'laugh' is the definition.
(I've seen this before)
'merriment no end after performance' is the wordplay.
'merriment' becomes 'glee' (glee is a kind of merriment).
'no end' means to remove the last letter.
'after' says to put letters next to each other.
'performance' becomes 'gig' (I've seen this before**).
'glee' with its final letter taken away is 'gle'.
'gle' after 'gig' is 'GIGGLE'.
'with' is the link.
(Other definitions for giggle that I've seen before include "Laugh foolishly" , "Titter" , "Foolish or nervous laugh" , "Nervous or silly laughter" , "Laugh affectedly" .)