Old Italian sure can't be adjusted (8)
I believe the answer is:
etruscan
'old italian' is the definition.
(I've seen this in another clue)
'sure can't be adjusted' is the wordplay.
'be adjusted' indicates anagramming the letters.
'sure'+'cant'='surecant'
'surecant' is an anagram of 'ETRUSCAN'.
(Other definitions for etruscan that I've seen before include "Of ancient Tuscany" , "Old Italian language" , "Of an ancient people of central Italy" , "Ancient language of W. Italy" , "Old person" .)