Mr. Silent turning out to be a singer (8)
I believe the answer is:
minstrel
'a singer' is the definition.
(I know that minstrel is a type of singer)
'mr silent turning out' is the wordplay.
'turning out' indicates an anagram.
'mr'+'silent'='mrsilent'
'mrsilent' with letters rearranged gives 'MINSTREL'.
'to be' is the link.
(Other definitions for minstrel that I've seen before include "Old travelling musician - a boy in Irish song" , "Strolling player" , "Singer of folk songs" , "Jongleur" , "Old song 'The ... boy to the wars has gone'" .)