They'd be crooked ones in Slade prison (5)
I believe the answer is:
deals
'they'd be crooked ones' is the definition.
I can't judge whether this definition defines the answer.
'slade prison' is the wordplay.
'slade' anagrams to 'DEALS'.
However, I am not sure how this is indicated.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for deals that I've seen before include "Hands around the cards" , "Business transactions" , "Passes cards around" , "Bargains" , "Trades" .)