A feature of Nero's name, or son, ‘Dicky (5,4)
I believe the answer is:
roman nose
'a feature' is the definition.
(I have seen 'outstanding feature' mean 'roman nose' so perhaps 'feature' could also mean 'roman nose')
'name or son 'dicky' is the wordplay.
''dicky' indicates an anagram (dicky can mean ill or non-functioning).
'name'+'or'+'son'='nameorson'
'nameorson' with letters rearranged gives 'ROMAN NOSE'.
'of nero's' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for roman nose that I've seen before include "outstanding feature" , "feature with bridge" , "personal feature" , "prominent Italian feature" .)