Cancel ex, repel change - beyond comparison (3,10)
I believe the answer is:
par excellence
'beyond comparison' is the definition.
(I've seen this before)
'cancel ex repel change' is the wordplay.
'change' indicates anagramming the letters.
'cancel'+'ex'+'repel'='cancelexrepel'
'cancelexrepel' anagrammed gives 'PAR EXCELLENCE'.
(Other definitions for par excellence that I've seen before include "Beyond compare" , "Superlative" , "Beyond comparison" , "Fine example" .)