Order Dutch treats, accepting Man Utd originally make the grade (3,3,7)
I believe the answer is:
cut the mustard
'make the grade' is the definition.
(thesaurus)
'order dutch treats accepting man utd originally' is the wordplay.
'order' indicates anagramming the letters.
'accepting' is an insertion indicator.
'originally' says to take the initial letters.
The first letters of 'man utd' is 'mu'.
'dutch'+'treats'='dutchtreats'
'dutchtreats' with letters rearranged gives 'cutthestard'.
'cutthestard' placed around 'mu' is 'CUT THE MUSTARD'.
(Other definitions for cut the mustard that I've seen before include "come up to expectations" , "impress" , "Make a favourable impression" , "Reach a required standard" , "do well enough" .)