"And so on and so forth" (3)
I believe the answer is:
etc
'and so on and so forth' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for etc that I've seen before include "And so on, briefly" , "And so on, in brief" , "'And the rest, in short (3)'" , "Etcetera (abbrev.)" , "And so forth (abbr)" .)