Bounder taking regular sojourn westward? (3)
I believe the answer is:
roo
'bounder' is the definition.
(short for kangaroo, something which bounds)
'regular sojourn westward?' is the wordplay.
'regular' indicates alternate letters.
'westward?' says the letters should be written backwards (I've seen 'westward' mean this).
The alternating letters of 'sojourn' are 'oor'.
'oor' back-to-front is 'ROO'.
'taking' acts as a link.
(Other definitions for roo that I've seen before include "Hopper" , "Small inhabitant of Hundred Acre Wood" , "short jumper" , "bounder" , "Young marsupial" .)