Laughing uncontrollably following theatre visit? (2,8)
I believe the answer is:
in stitches
'laughing uncontrollably' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
(Other definitions for in stitches that I've seen before include "extremely amused" , "much affected by comedy?" , "Helpless with laughter" , "as one may be on leaving the theatre?" , "you may be laughing" .)