Funny bone with a large diameter (6)
I believe the answer is:
ribald
'funny' is the definition.
Both the answer and definition are adjectives. Maybe you can see an association between them that I don't see?
'bone with a large diameter' is the wordplay.
'bone' becomes 'rib' (rib is a type of bone).
'with' means one lot of letters go next to another.
'large' becomes 'L' (eg in clothes sizes).
'diameter' becomes 'd' (mathematics).
'rib'+'a'+'l'+'d'='RIBALD'
Can you help me to learn more?
(Other definitions for ribald that I've seen before include "Irreverent" , "Humourous in vulgar way" , "Coarsely mocking" , "Indecent" , "Obscene" .)