And the rest, much being missing (3)
I believe the answer is:
etc
'and the rest' is the definition.
(et cetera)
'much being missing' is the wordplay.
'much' means to remove the last letter (much but not all of the word).
'being' becomes 'ex' (ex is a kind of being).
'missing' becomes 'tc' (I can't explain this - if you can you should believe this answer much more).
'ex' with its last letter taken away is 'e'.
'e'+'tc'='ETC'
Can you help me to learn more?
(Other definitions for etc that I've seen before include "Etcetera (abbrev.)" , "'And the rest, in short (3)'" , "And so on, briefly" , "And so forth (abbr)" , "And so on, in brief" .)