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