Eat in dining establishment (6)
I believe the answer is:
ingest
'eat' is the definition.
(thesaurus)
'in dining establishment' is the wordplay.
'in' indicates a hidden word.
'INGEST' can be found hidden inside 'dining establishment'.
(Other definitions for ingest that I've seen before include "Consume food" , "Eat - gin set (anag)" , "How to take courses" , "Gets in (anag.)" , "Scoff" .)