Briefest (8)
I believe the answer is:
shortest
'briefest' is the definition.
('short' can be similar in meaning to 'brief')
This is all the clue.
(Other definitions for shortest that I've seen before include "Least in length" , "Most vertically challenged" , "'The longest way round is the ... way home' (proverb)" , "The longest way round can often be the ........ way home" , "Lowest in stature" .)