This writer's mellow still (5)
I believe the answer is:
image
'still' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'this writer's mellow' is the wordplay.
'this writer's' becomes 'im' ('writer's' could mean 'the crossword setter is').
'mellow' becomes 'age' (both can mean to mature).
'im'+'age'='IMAGE'
Can you help me to learn more?
(Other definitions for image that I've seen before include "Likeness, might be spitting" , "Likeness or mental picture" , "Public impression" , "Picture; simile" , "Representation of person or thing" .)