A bookkeeper's sign preceding revolutionary Iran (9)
I believe the answer is:
librarian
'a bookkeeper's' is the definition.
(thesaurus)
'sign preceding revolutionary iran' is the wordplay.
'sign' becomes 'libra' (sign of the zodiac).
'preceding' says to put letters next to each other.
'revolutionary' indicates anagramming the letters.
'iran' is an anagram of 'rian'.
'libra'+'rian'='LIBRARIAN'
(Other definitions for librarian that I've seen before include "Book keeper" , "employee in Reading office?" , "lender" , "One dealing with books" , "Bibliothecary" .)