Brave bishop gets elderly (4)
I believe the answer is:
bold
'brave' is the definition.
(similar in meaning)
'bishop gets elderly' is the wordplay.
'bishop' becomes 'B' (chess abbreviation).
'gets' means one lot of letters go next to another.
'elderly' becomes 'old' (similar in meaning).
'b'+'old'='BOLD'
(Other definitions for bold that I've seen before include "Intrepid" , "No chicken" , "Valiant" , "Typeface with thick heavy lines" , "like Ben Battle" .)