...in roof angle (3)
I believe the answer is:
hip
This might be a double definition.
'in' is the first definition.
(both can mean fashionable)
'roof angle' is the second definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
Can you help me to learn more?
(Other definitions for hip that I've seen before include "Trendy bodily joint?" , "Fruit of the wild rose (3)" , "Side of body - very sophisticated" , "Cool < fruit" , "In slang, trendy or stylish like body joint" .)