Stupendous (7)
I believe the answer is:
amazing
'stupendous' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for amazing that I've seen before include "Astounding, awe-inspiring" , "Hymn that 'sav'd a wretch like me'?" , "Prodigious" , "description of Grace?" , "Filling with wonder, a huge surprise" .)