Bishop, aged yet brave (4)
I believe the answer is:
bold
'brave' is the definition.
(associated in meaning)
'bishop aged' is the wordplay.
'bishop' becomes 'B' (chess abbreviation).
'aged' becomes 'old' (similar in meaning).
'b'+'old'='BOLD'
'yet' acts as a link.
(Other definitions for bold that I've seen before include "Confident, daring" , "Like heavy type" , "Brave" , "No chicken" , "Daring, maybe impudent" .)