Put off job organising open day (9)
I believe the answer is:
postponed
'put off' is the definition.
(I've seen this before)
'job organising open day' is the wordplay.
'job' becomes 'post' (post is a kind of job).
'organising' indicates an anagram.
'day' becomes 'd' (abbreviation for day).
'open' with letters rearranged gives 'pone'.
'post'+'pone'+'d'='POSTPONED'
(Other definitions for postponed that I've seen before include "delayed" , "Put off" , "Deferred" .)