Finish off Sanctus composed in Italian (6)
I believe the answer is:
tuscan
'italian' is the definition.
(Tuscan is an example)
'finish off sanctus composed' is the wordplay.
'finish off' means to remove the last letter.
'composed' is an anagram indicator.
'sanctus' with its last letter removed is 'sanctu'.
'sanctu' is an anagram of 'TUSCAN'.
'in' is the link.
(Other definitions for tuscan that I've seen before include "Standard Italian" , "Relating to a region of Italy" , "From a central Italian region" , "Italian inhabitant of what was once Etruria" , "European" .)