One leading tributes to expert quietly leaves (11)
I believe the answer is:
toastmaster
'one leading tributes to expert quietly leaves' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'one leading tributes to expert' is the wordplay.
'one leading tributes' becomes 'toast' (I am not sure about this - if you are sure you should believe this answer much more).
'to expert' becomes 'master' (master is a kind of expert).
'toast'+'master'='TOASTMASTER'
Can you help me to learn more?
(Other definitions for toastmaster that I've seen before include "Address given after my introduction" , "Master of ceremonies at a banquet" , "Official at social event" , "Organizer of tributes" , "one announces at dinner" .)