Philosopher tours east, warning of danger (6)
I believe the answer is:
beacon
'warning of danger' is the definition.
(a light used as a warning signal)
'philosopher tours east' is the wordplay.
'philosopher' becomes 'Bacon' (Francis Bacon).
'tours' indicates putting letters inside (to tour can mean to go around).
'east' becomes 'e' (synonyms).
'bacon' placed around 'e' is 'BEACON'.
(Other definitions for beacon that I've seen before include "This may serve as a warning" , "warning to others" , "Raised signal fire or light" , "Warning light on hill or cliff" , "Warning or guiding device" .)