Rag terrible actor fellow (6)
I believe the answer is:
graham
'fellow' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see a link between them that I can't see?
'rag terrible actor' is the wordplay.
'terrible' is an anagram indicator.
'actor' becomes 'ham' (ham actor is a kind of actor).
'rag' is an anagram of 'gra'.
'gra'+'ham'='GRAHAM'
Can you help me to learn more?
(Other definitions for graham that I've seen before include "Novelist, who wrote..." , "Alexander - Bell, Scottish-born inventor" , "--- Hill, 60s motor-racing champion" , "Land" , "town in South Africa takes the > biscuits" .)