Happen; eventuate (5)
I believe the answer is:
occur
I believe this clue is a double definition.
'happen' is the first definition.
(synonyms)
'eventuate' is the second definition.
(I've seen this in another clue)
(Other definitions for occur that I've seen before include "Come to pass" , "crop up" , "Happen, transpire" , "exist" , "Go on" .)