Mature answer good by news boss (4)
I believe the answer is:
aged
'mature' is the definition.
(similar in meaning)
'answer good by news boss' is the wordplay.
'answer' becomes 'a' (abbreviation eg in Q and A).
'good' becomes 'g' (abbreviation).
'by' says to put letters next to each other.
'news boss' becomes 'ed' (I've seen this in other clues).
'a'+'g'+'ed'='AGED'
(Other definitions for aged that I've seen before include "Long in the tooth" , "Time-worn" , "not a modern copy" , "way over the hill" , "Getting on" .)