I'm unclear about using digits (9)
I believe the answer is:
numerical
'i'm unclear about using digits' is the definition.
I can't judge whether this defines the answer.
'i'm unclear about' is the wordplay.
'about' indicates anagramming the letters.
'im'+'unclear'='imunclear'
'imunclear' is an anagram of 'NUMERICAL'.
Can you help me to learn more?
(Other definitions for numerical that I've seen before include "Relating to such as 9 or 123" , "like characters, perhaps" , "of digits" , "Muriel can (anag)" , "Using arithmetic values" .)