Arcane secret I spread around Ohio (8)
I believe the answer is:
esoteric
'arcane' is the definition.
(similar in meaning)
'secret i spread around ohio' is the wordplay.
'spread' is an anagram indicator.
'around' means one lot of letters goes inside another.
'ohio' becomes 'o'.
'secret'+'i'='secreti'
'secreti' is an anagram of 'esteric'.
'esteric' going around 'o' is 'ESOTERIC'.
(Other definitions for esoteric that I've seen before include "Highly specialised" , "Intelligible only with special knowledge" , "needing privy" , "Inner - secret" , "Secret kind of coteries" .)