With which to open hostilities? (4)
I believe the answer is:
shot
'with which to open hostilities?' is the definition.
I can't judge whether this defines the answer.
'with which to open' is the wordplay.
'with' says to put letters next to each other.
'which' becomes 'sho' (I am not sure about this - if you are sure you should believe this answer much more).
'open' suggests taking the first letters (I've seen 'opens' mean this).
The initial letter of 'to' is 't'.
'sho'+'t' is 'SHOT'.
Can you help me to learn more?
(Other definitions for shot that I've seen before include "Fired from a weapon" , "Woven in different colours; attempt to score" , "Photo; try" , "Knackered" , "injured or killed?" .)