Public perception: this writer is mature (5)
I believe the answer is:
image
'public perception' is the definition.
(I've seen this before)
'this writer is mature' is the wordplay.
'this writer is' becomes 'I'm' (I am - referring to the crossword setter).
'mature' becomes 'age' (synonyms).
'im'+'age'='IMAGE'
(Other definitions for image that I've seen before include "Likeness of person or thing" , "Optical counterpart in mirror" , "Photo or likeness" , "External impression" , "Simile, metaphor" .)