Division apparent in war machine (3)
I believe the answer is:
arm
'division' is the definition.
(arm is a kind of division)
'apparent in war machine' is the wordplay.
'apparent in' indicates a hidden word (the answer can be seen in the clue).
'ARM' is hidden in the letters of 'war machine'.
(Other definitions for arm that I've seen before include "Upper limb" , "Shoulder to fingertip" , "Equip with weapons" , "Equip with a limb" , "ready for war" .)