Occur (6)
'occur' is the definition.
(I know that occur can be written as happen)
This is all the clue.
(Other definitions for happen that I've seen before include "Turn out" , "Take place" , "perhaps for Yorkshire" , "Occur" , "Come to pass" .)
'occur' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for exist that I've seen before include "Scrape by" , "Live" , "Have objective reality" , "Be alive" , "Survive" .)
'occur' is the definition.
(arising is a kind of occuring)
This is all the clue.
(Other definitions for arise that I've seen before include "Occur; stand up" , "Originate; get up" , "Spring - get up" , "Get up or come up" , "Become apparent" .)