Took the attitude that dopes shouldn't be so silly (5)
I believe the answer is:
posed
'took the attitude' is the definition.
The definition and answer can be both to do with communicating as well as being past participle verbs.
Maybe you can see an association between them that I don't see?
'dopes shouldn't be so silly' is the wordplay.
'dopes' can be anagrammed to 'POSED'.
However, I'm not sure how the anagram is indicated.
'that' is the link.
Can you help me to learn more?
(Other definitions for posed that I've seen before include "Presented (a problem)" , "Presented (a question)" , "Took a stance" , "Modelled" , "Sat (for artist)" .)