Idea caught on with a record in court (7)
I believe the answer is:
concept
'idea' is the definition.
(concept is a kind of idea)
'caught on with a record in court' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'with' says to put letters next to each other.
'a record' becomes 'ep' (abbreviation for extended play record).
'in' indicates putting letters inside.
'court' becomes 'ct' (abbreviation used in road names).
'ep' going within 'ct' is 'cept'.
'c'+'on'+'cept'='CONCEPT'
(Other definitions for concept that I've seen before include "Abstract idea; mental picture" , "Notion" , "Abstract or general idea" , "Product of the mind" .)