Manna from heaven! (7)
I believe the answer is:
godsend
'manna from heaven' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for godsend that I've seen before include "Very opportune thing" , "Boon - blessing" , "The relief" , "Unexpected help" , "A piece of unexpected good fortune - despatched from above?" .)