Practised diner at buffet (7)
I believe the answer is:
trained
'practised' is the definition.
(thesaurus)
'diner at buffet' is the wordplay.
'buffet' is an anagram indicator (I've seen 'buffeted' mean this).
'diner'+'at'='dinerat'
'dinerat' anagrammed gives 'TRAINED'.
(Other definitions for trained that I've seen before include "Prepared for a task or career" , "Worked out" , "Prepared for race" , "Coached" , "ran along track" .)