One no longer beating person offering clarification (9)
I believe the answer is:
expounder
'person offering clarification' is the definition.
(someone who expounds or explains)
'one no longer beating' is the wordplay.
'one no longer' becomes 'ex' (prefix meaning former or onetime).
'beating' becomes 'pounder' (I can't justify this - if you can you should believe this answer much more).
'ex'+'pounder'='EXPOUNDER'
(Other definitions for expounder that I've seen before include "interpreter" , "One fully describes" .)