Event (10)
'event' is the definition.
(occasion is a kind of event)
This is the entire clue.
(Other definitions for occasion that I've seen before include "A special event, or the time it happens" , "incident" , "excuse for > special ceremony" , "call" , "Opportunity" .)
'event' is the definition.
(I know that occurrence is a type of event)
This is all the clue.
(Other definitions for occurrence that I've seen before include "Happening" , "Event" .)