Strengthened the appearance of being polished (5)
I believe the answer is:
waxed
This could be a double definition.
'strengthened the appearance' is the first definition.
The answer and definition can be both related to change as well as being past participle verbs.
Maybe you can see a link between them that I can't see?
'being polished' is the second definition.
Both the definition and answer are adjectives. Maybe they are linked in a way I don't understand?
'of' is the link.
Can you help me to learn more?
(Other definitions for waxed that I've seen before include "Increased in phase" , "Became fuller" , "Grew larger" .)