Bright chap having friendly fight with king (5)
I believe the answer is:
spark
'bright chap' is the definition.
The answer and definition can be both natural objects as well as being singular nouns.
Maybe you can see a link between them that I don't see?
'friendly fight with king' is the wordplay.
'friendly fight' becomes 'spar' (sparring is a kind of fighting. I am not sure about the 'friendly' bit.).
'with' is a charade indicator (letters next to each other).
'king' becomes 'K' (chess abbreviation).
'spar'+'k'='SPARK'
'having' acts as a link.
Can you help me to learn more?
(Other definitions for spark that I've seen before include "Fiery particle" , "Tiny, red-hot particle" , "Fragment of a burning substance" , "Bright flash; ignite" , "bit of fire?" .)