A business turns up with a fad beyond the bounds of knowledge (6)
I believe the answer is:
occult
'beyond the bounds of knowledge' is the definition.
I can't tell whether this defines the answer.
'a business turns up with a fad' is the wordplay.
'a business' becomes 'co' (short for company).
'turns up' shows that the letters should be reversed in order.
'with' means one lot of letters go next to another.
'a fad' becomes 'cult' (synonyms).
'co' back-to-front is 'oc'.
'oc'+'cult'='OCCULT'
Can you help me to learn more?
(Other definitions for occult that I've seen before include "Characteristic of supernatural phenomena" , "Mysticism" , "Secret - paranormal" , "Mystical, involving the supernatural" , "Involving the supernatural or magical" .)