A short test in lobbies (5)
I believe the answer is:
atria
'lobbies' is the definition.
(plural of atrium, type of hall or lobby)
'a short test' is the wordplay.
'short' means to remove the last letter.
'test' becomes 'trial' (synonyms).
'trial' with its last letter taken off is 'tria'.
'a'+'tria'='ATRIA'
'in' acts as a link.
(Other definitions for atria that I've seen before include "Central courtyards" , "Covered courts" , "Central courts, halls" , "Central courts (in ancient Rome or shopping arcades)" , "Open-roofed entrance halls (Roman) - glass-roofed central halls (modern)" .)