Switch positions periodically (8)
I believe the answer is:
offandon
'positions periodically' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'switch' is the wordplay.
I cannot really see how this works, but
'switch' could be 'off' (I've seen this in another clue) and 'off' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for offandon that I've seen is " Occasionally".)