Stick used in returning assault (3)
I believe the answer is:
gum
'stick' is the definition.
(gum can mean to glue or stick)
'used in returning assault' is the wordplay.
'used in' says to take the centre (the letters used on the inside of the word).
'returning' becomes 'going home' (going home is a kind of returning).
'assault' becomes 'um' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The middle of 'goinghome' is 'g'.
'g'+'um'='GUM'
Can you help me to learn more?
(Other definitions for gum that I've seen before include "Stuff to chew" , "Adhesive for chewing" , "Eg, a eucalyptus" , "Gingeva is its technical name" , "To stick with adhesive" .)