Exercise, having ingested rich sauce somewhere in Czech Republic (6)
I believe the answer is:
prague
'somewhere in czech republic' is the definition.
'exercise having ingested rich sauce' is the wordplay.
'exercise' becomes 'pe' (Physical Education).
'having ingested' indicates putting letters inside.
'rich sauce' becomes 'ragu'.
'pe' enclosing 'ragu' is 'PRAGUE'.
(Other definitions for prague that I've seen before include "Gear up for this European city" , "Rather quiet" , "Czech Republic's capital" , "Capital city of Czech Republic" , "European capital" .)