Strikes fear into criminal divisions (6)
I believe the answer is:
alarms
'strikes fear' is the definition.
Although both the answer and definition are verbs in their -s form, I don't see how one could define the other.
'criminal divisions' is the wordplay.
'criminal' becomes 'al' (I can't justify this - if you can you should give a lot more credence to this answer).
'divisions' becomes 'arms' (arm is a kind of division).
'al'+'arms'='ALARMS'
'into' acts as a link.
Can you help me to learn more?
(Other definitions for alarms that I've seen before include "Frightens, scares" , "Scares or startles" , "rattles" , "Disturbs" , "Clocks that wake sleepers" .)