Funny business caught on motorway (5)
I believe the answer is:
comic
'funny' is the definition.
(comic can mean funny or humorous)
'business caught on motorway' is the wordplay.
'business' becomes 'co' (short for company).
'caught' becomes 'c' (cricket abbreviation).
'on' says to put letters next to each other.
'motorway' becomes 'MI' (resembles Mc, English motorway).
'c' after 'mi' is 'mic'.
'co'+'mic'='COMIC'
(Other definitions for comic that I've seen before include "Garden perhaps" , "Funny; comedian" , "Funny entertainer, often stand-up" , "Funny man, maybe stand-up" , "Stand-up possibly" .)