They happen to get sent off at a quarter to five (6)
I believe the answer is:
events
'they happen' is the definition.
(I've seen this before)
'sent off at a quarter to five' is the wordplay.
'off' indicates an anagram.
'at' means one lot of letters go next to another (I've seen this in other clues).
'a quarter' becomes 'e'.
'to five' becomes 'v' (roman numeral).
'sent' is an anagram of 'ents'.
'e'+'v'='ev'
'ents' put after 'ev' is 'EVENTS'.
'to get' acts as a link.
(Other definitions for events that I've seen before include "competition" , "Episodes" , "Planned social occasions" , "Occurrences, happenings" , "Horse-riding competitions" .)