Backing an opponent of violence, mostly with King in spirit (5)
I believe the answer is:
vodka
'spirit' is the definition.
(I've seen this before)
'backing an opponent of violence mostly with king' is the wordplay.
'backing' is a reversal indicator.
'an opponent of violence' becomes 'dove' (as opposed to a hawk).
'mostly' means to remove the last letter (most but not all of the word).
'with' means one lot of letters go next to another.
'king' becomes 'ka' (I am not sure about this - if you are sure you should believe this answer much more).
'dove' with its last letter taken away is 'dov'.
'dov' written backwards gives 'vod'.
'vod'+'ka'='VODKA'
'in' is the link.
Can you help me to learn more?
(Other definitions for vodka that I've seen before include "Spirit made from rye, wheat or potatoes" , "Colourless alcohol" , "shot?" , "Russian "little water"" , "Strong drink" .)