Daring bishop has aged (4)
I believe the answer is:
bold
'daring' is the definition.
(I've seen this in another clue)
'bishop has aged' is the wordplay.
'bishop' becomes 'B' (abbreviation for bishop in chess).
'has' is a charade indicator (letters next to each other).
'aged' becomes 'old' (similar in meaning).
'b'+'old'='BOLD'
(Other definitions for bold that I've seen before include "Thick and heavy (type)" , "Like heavy type" , "Confident, daring" , "Courageous, confident" , "Typeface with thick heavy lines" .)