Common person seen in theatre, very mannered (8)
I believe the answer is:
everyman
'common person' is the definition.
Both the answer and definition are singular nouns.
Maybe you can see an association between them that I can't see?
'in theatre very mannered' is the wordplay.
'in' says the answer is hidden in the clue.
'EVERYMAN' is hidden within 'theatre very mannered'.
'seen' acts as a link.
Can you help me to learn more?
(Other definitions for everyman that I've seen before include "Mystery play character" , "Average Joe" , "Mr Average" , "Old morality play" , "Anybody - the hero of a morality play - Observer crossword" .)