Some fallen idol rises a god (4)
I believe the answer is:
odin
'a god' is the definition.
(Norse god)
'some fallen idol rises' is the wordplay.
'some' says the answer is hidden in the clue (some parts of the word are used).
'rises' says the letters should be written backwards.
'nido' is hidden within 'fallen idol'.
'nido' reversed gives 'ODIN'.
(Other definitions for odin that I've seen before include "mythological personage" , "In Scandinavian myth the supreme god and creator" , "an all-powerful one" , "King of Norse gods" , "I nod to the Norse deity" .)