Switch positions intermittently (3,3,2)
(Other definitions for off and on that I've seen before include "Now and then, stop and start" , "Switch options" , "Occasionally" , "sometimes" , "the two sides at the Oval are this" .)
This clue is a double definition.
'switch positions' is the first definition.
(I've seen this before)
'intermittently' is the second definition.
(I've seen this before)
(Other definitions for on and off that I've seen before include "the two sides at Old Trafford?" , "From time to time, not continually" , "Now and then, starting and stopping" , "Perhaps switch positions" , "Intermittently" .)