Kind chap in cast (6)
I believe the answer is:
humane
'kind' is the definition.
(similar in meaning)
'chap in cast' is the wordplay.
'chap' becomes 'Man' (chap can mean a man).
'in' is an insertion indicator.
'cast' becomes 'hue' (both can mean the colour of something).
'man' inserted into 'hue' is 'HUMANE'.
(Other definitions for humane that I've seen before include "Showing compassion or consideration for others" , "Kindly or merciful" , "Inflicting minimal pain" , "Kind-hearted and compassionate" , "Kindly and compassionate" .)