Alien crate exploding with energy and so forth (8)
I believe the answer is:
etcetera
'and so forth' is the definition.
(synonyms)
'alien crate exploding with energy' is the wordplay.
'alien' becomes 'et' (extra terrestrial).
'exploding with' indicates anagramming the letters.
'energy' becomes 'e' (physics symbol as in E=mc2).
'crate' with its letters anagrammed with 'e' can make 'cetera'.
'et'+'cetera'='ETCETERA'
(Other definitions for etcetera that I've seen before include "And the rest" , "and the like" .)