Heaven on Earth contains nothing (4)
I believe the answer is:
none
'nothing' is the definition.
(I've seen this in another clue)
'heaven on earth contains' is the wordplay.
'contains' indicates the answer is hidden within the clue.
'NONE' is hidden within 'heaven on earth'.
(Other definitions for none that I've seen before include "hour of prayer" , "Nobody - nothing" , "Zero" , "Not a thing or person" , "Not a soul" .)