Noble number (5)
I believe the answer is:
count
I believe this clue is a double definition.
'noble' is the first definition.
(count is a type of aristocrat)
'number' is the second definition.
(I know that number can be written as count)
(Other definitions for count that I've seen before include "Nobleman - tell how many" , "regard" , "Matter to consider" , "Include; nobleman" , "earl abroad" .)