Brute heading off in one direction (4)
I believe the answer is:
east
'one direction' is the definition.
(east is a kind of direction)
'brute heading off' is the wordplay.
'brute' becomes 'beast' ('beast' can be a synonym of 'brute').
'heading off' means to remove the first letter.
'beast' with its first letter removed is 'EAST'.
'in' is the link.
(Other definitions for east that I've seen before include "4 dn 17 dn" , "Airport near Derby" , "Asia" , "course" , "Direction taken when going from the US towards Ireland" .)