Remarkable things: a mixture of hope 'n' amen! (9)
I believe the answer is:
phenomena
'remarkable things' is the definition.
(I've seen this before)
'a mixture of hope n amen' is the wordplay.
'a mixture of' is an anagram indicator (letters mixed up).
'hope'+'n'+'amen'='hopenamen'
'hopenamen' with letters rearranged gives 'PHENOMENA'.
(Other definitions for phenomena that I've seen before include "spectacles" , "He-man open to remarkable things or wonders" , "Things sensed" , "wondrous things" , "Unusual developments" .)