Hell's got this mobster in for straightening out (9)
I believe the answer is:
brimstone
'hell's' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'this mobster in for straightening out' is the wordplay.
'mobster in' can be anagrammed to 'BRIMSTONE'.
However, I'm not sure how this is indicated.
'got' acts as a link.
Can you help me to learn more?
(Other definitions for brimstone that I've seen before include "It robs men (anag) - old word for sulphur" , "Old name for sulphur" , "Sulphur (when associated with hellfire)" , "Fire partner" , "Biblical sulphur that rained with fire on evil cities" .)