Light playing in arcade (8)
I believe the answer is:
radiance
'light' is the definition.
(radiance is a kind of light)
'playing in arcade' is the wordplay.
'playing' is an anagram indicator.
'in'+'arcade'='inarcade'
'inarcade' is an anagram of 'RADIANCE'.
(Other definitions for radiance that I've seen before include "Effulgence" , "Great joy" , "Glowing quality" , "Joyful splendour" , "shine" .)