After fighting me king is more friendly (6)
I believe the answer is:
warmer
'more friendly' is the definition.
('warm' is associated in meaning with 'friendly')
'after fighting me king' is the wordplay.
'after' is a charade indicator (letters next to each other).
'fighting' becomes 'war'.
'king' becomes 'R' (abbreviation of Latin rex).
'war' next to 'me' is 'warme'.
'warme'+'r'='WARMER'
'is' acts as a link.
(Other definitions for warmer that I've seen before include "Having a higher temperature" , "Closer to target" , "Less cool" , "Less cold" , "Containing more heat" .)