A photo finish (5)
I believe the answer is:
gloss
This might be a double definition.
'a photo' is the first definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'finish' is the second definition.
(I've seen this before)
Can you help me to learn more?
(Other definitions for gloss that I've seen before include "Very shiny finish" , "Render plausible" , "Shiny surface" , "Surface shine" , "phrase's explanation" .)