Working, then not, from time to time (2,3,3)
I believe the answer is:
on and off
'from time to time' is the definition.
(I've seen this before)
'working then not' is the wordplay.
I cannot really understand how this works, but
'working' could be 'on' (on can mean working or activated) and 'on' is located in the answer.
'then' could be 'and' (synonyms) and 'and' is present in the answer.
'not' could be 'o' (I've seen this in other clues) and 'o' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for on and off that I've seen before include "From time to time, not continuously" , "Switch choices" , "Perhaps switch positions" , "the two sides at Old Trafford?" , "periodically" .)