Avoid weapons? Not half (4)
I believe the answer is:
miss
'avoid' is the definition.
(missing is a kind of avoiding)
'weapons? not half' is the wordplay.
'weapons?' becomes 'missiles' (missile is a kind of weapon).
'not half' suggests halving the letters.
'missiles' halved is 'MISS'.
(Other definitions for miss that I've seen before include "Fail to see or hit" , "Feel the loss of - schoolgirl" , "Teacher" , "Fail to meet - girl" , "Single girl" .)