Hard one to crack so ran it past expert (9)
I believe the answer is:
historian
'past expert' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'hard one to crack so ran it' is the wordplay.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'one' becomes 'i' (Roman numeral).
'to crack' indicates an anagram.
'so'+'ran'+'it'='soranit'
'soranit' anagrammed gives 'storian'.
'h'+'i'+'storian'='HISTORIAN'
Can you help me to learn more?
(Other definitions for historian that I've seen before include "Past master" , "chronicler" , "student of the past" , "One sort of academic" , "So thin air suits recorder and analyst of past events" .)