Grand people's prayer (5)
I believe the answer is:
'prayer' is the definition.
(I know that grace is a type of prayer)
'grand people's' is the wordplay.
'grand' becomes 'g' (G is short for grand as in a thousand).
'people' becomes 'race' (people can mean a national group or race).
(Other definitions for grace that I've seen before include "beauty of movement" , "Prayer of thanks before/after a meal" , "'Amazing - - '" , "Elegance; girl's name" , "cricketing great" .)