Run into thicket to laugh uncontrollably (6)
I believe the answer is:
corpse
'laugh uncontrollably' is the definition.
(as in corpsing during a theatrical performance)
'run into thicket' is the wordplay.
'run' becomes 'r' (cricket abbreviation).
'into' is an insertion indicator.
'thicket' becomes 'copse' (synonyms).
'r' going within 'copse' is 'CORPSE'.
'to' is the link.
(Other definitions for corpse that I've seen before include "Cadaver, dead person" , "Dead bodies" , "Roof beam" , "Dead body" .)