Most unusual alteration in set grants (9)
I believe the answer is:
strangest
'most unusual' is the definition.
(I've seen this before)
'alteration in set grants' is the wordplay.
'set grants' anagrams to 'STRANGEST'.
Though, I am unsure how this is indicated.
Can you help me to learn more?
(Other definitions for strangest that I've seen before include "Most unusual, oddest" , "Most remarkable" , "Most unusual or odd" , "Most out of the ordinary and unexpected" , "Most peculiar" .)