As a joke, created a cult – and just in time (8)
I believe the answer is:
punctual
'in time' is the definition.
('punctual' can be similar in meaning to 'in time')
'as a joke created a cult and' is the wordplay.
'as a joke' becomes 'pu' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'created' indicates an anagram (I've seen 'create' mean this).
'and' becomes 'n' (common abbreviation for 'and').
'a'+'cult'+'n'='acultn'
'acultn' is an anagram of 'nctual'.
'pu'+'nctual'='PUNCTUAL'
'just' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for punctual that I've seen before include "Happening at the agreed time" , "Exactly on time" , "Arriving on time" , "Always on time for appointments" , "Bang on time" .)