Test covers part of town bypass perhaps (7)
I believe the answer is:
orbital
'town bypass perhaps' is the definition.
(as in an orbital road around a town)
'test covers part' is the wordplay.
'test' becomes 'oral' (oral is a type of examination).
'covers' is an insertion indicator.
'part' becomes 'bit' (both mean a piece of something).
'oral' placed around 'bit' is 'ORBITAL'.
'of' acts as a link.
(Other definitions for orbital that I've seen before include "Of road, circling a town" , "Circular, like the M25" , "Like a sort of road" , "(Of road) skirting town" , "Going round the world" .)