A snack regularly being covered in nuts is not OK! (8)
I believe the answer is:
sanction
'ok' is the definition.
(I know this)
'a snack regularly being covered in nuts is not' is the wordplay.
'a snack regularly' becomes 'anc' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'being covered in' indicates putting letters inside.
'nuts' indicates an anagram (nuts can mean crazy).
'is'+'not'='isnot'
'isnot' with letters rearranged gives 'stion'.
'anc' placed inside 'stion' is 'SANCTION'.
Can you help me to learn more?
(Other definitions for sanction that I've seen before include "Ratification" , "Authorisation" , "Give official approval or attach a penalty to" , "Allow; punish" , "Official approval (for an action)" .)