Crack up (5)
'crack up?' is the definition.
(cracking up is a kind of extolling)
This is the entire clue.
(Other definitions for extol that I've seen before include "Praise - honour" , "Praise enthusiastically" , "Highly commend" , "trumpet" , "Glorify - honour" .)
'crack up' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for laugh that I've seen before include "Sound of mirth" , "Cachinnate" , "scream?" , "Break up" , "a ridiculous thing" .)