Brief trip (3)
I believe the answer is:
hop
'brief trip' is the definition.
(I have seen 'Short trip ' mean 'hop' so perhaps 'trip' could also mean 'hop'; 'brief' asks for an abbreviation)
This is the entire clue.
(Other definitions for hop that I've seen before include "Skip; beer flavouring ingredient" , "Short trip" , "Leap on one leg" , "Dancing party (informal)" , "It's used in brewing" .)