Our hall is regularly used for exam (4)
I believe the answer is:
oral
'for exam' is the definition.
(spoken academic test)
'our hall is regularly' is the wordplay.
'is regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'our'+'hall'='ourhall'
The alternating letters of 'ourhall' are 'ORAL'.
'used' acts as a link.
(Other definitions for oral that I've seen before include "Concerning the mouth" , "Mouth-related" , "Vocal test" , "Spoken - examination" , "Related to the mouth" .)