Original sign (7)
I believe the answer is:
initial
I believe this clue is a double definition.
'original' is the first definition.
(thesaurus)
'sign' is the second definition.
(initial is a kind of sign)
(Other definitions for initial that I've seen before include "Start of name" , "Primary" , "Beginning - first letter" , "Original; beginning" , "Occurring at the beginnng" .)