Happen to come later (5)
I believe the answer is:
I believe this is a double definition.
'happen' is the first definition.
(I've seen this before)
'come later' is the second definition.
(I've seen this in another clue)
'to' acts as a link.
(Other definitions for ensue that I've seen before include "Follow afterwards" , "Result in a particular way" , "Come about, result in" , "Transpire" , "Turn out" .)