Not the sort of conversation associated with crooks (8,4)
I believe the answer is:
straight talk
'not the sort' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'conversation associated with crooks' is the wordplay.
'conversation' becomes 'talk' (talk is a kind of conversation).
'associated with' is a charade indicator (letters next to each other).
'crooks' becomes 'straight' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'talk' after 'straight' is 'STRAIGHT TALK'.
'of' is the link.
Can you help me to learn more?
(Another definition for straight talk that I've seen is " Candid conversation".)