Pass our plan for interior decoration (6,6)
I believe the answer is:
colour scheme
'interior decoration' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'pass our plan' is the wordplay.
'pass' becomes 'col' (col is a term for a mountain pass).
'plan' becomes 'scheme' (scheming is a kind of planning).
'col'+'our'+'scheme'='COLOUR SCHEME'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for colour scheme that I've seen before include "Arrangement or combination of tones and hues" , "Interior decoration plan" , "dictating arrangements for the flat, say" .)