Stout Russian teacher originally in old college (6)
I believe the answer is:
portly
'stout' is the definition.
('portly' can be a synonym of 'stout')
'russian teacher originally in old college' is the wordplay.
'originally' suggests taking the first letters.
'in' indicates putting letters inside.
'old college' becomes 'poly' (polytechnic).
The first letters of 'russian teacher' is 'rt'.
'rt' placed within 'poly' is 'PORTLY'.
(Other definitions for portly that I've seen before include "Rotund" , "Rather fat" , "Stout and dignified" , "with corporation" , "Somewhat overweight" .)