Distinction (4)
'distinction' is the definition.
(I know that distinction can be written as note)
This is the entire clue.
(Other definitions for note that I've seen before include "mention" , "Record; memo" , "Symbol in a score" , "Short message; piano key" , "Traitor" .)
(Other definitions for calibre that I've seen before include "gifts" , "measure of a bore" , "Ability; barrel diameter" , "Bullet size" , "Diameter of a gun barrel" .)