Wild lion scared no one; certainly not him (9)
I believe the answer is:
androcles
'certainly not him' is the definition.
The definition suggests a singular noun which matches the answer.
'wild lion scared no one' is the wordplay.
'wild' is an anagram indicator.
'no' indicates named letters should be taken away.
'one' becomes 'i' (Roman numeral).
'lion'+'scared'='lionscared'
'lionscared' with 'i' taken out is 'lonscared'.
'lonscared' with letters rearranged gives 'ANDROCLES'.
Can you help me to learn more?
(Other definitions for androcles that I've seen before include "He played a lion-tamer" , "Shaw play: -- and the Lion" .)