Laugh had not finished twice (2-2)
I believe the answer is:
ha-ha
'laugh' is the definition.
(I know that ha-ha is a type of laugh)
'had not finished twice' is the wordplay.
'not finished' means to remove the last letter.
'twice' shows that letters should be duplicated.
'had' with its last letter taken off is 'ha'.
'ha' doubled is 'HA-HA'.
(Other definitions for ha-ha that I've seen before include "Ditch with wall in it - sounds funny" , "Ditch with wall in it - sounds merry" , "Sunken fence or wall" , "Ditch with a wall in it - that's a laugh" , "Sunken barrier" .)