Raising agent, heading off in this direction? (4)
I believe the answer is:
east
'this direction?' is the definition.
(east is a kind of direction)
'raising agent heading off' is the wordplay.
'raising agent' becomes 'yeast' (I've seen this before).
'heading off' means to remove the first letter.
'yeast' with its initial letter removed is 'EAST'.
'in' is the link.
(Other definitions for east that I've seen before include "Direction of the Orient" , "On most maps it's right!" , "Bearing of 90 degrees" , "Asia" , "bridge-player" .)