Pocketing a brown, so coming to black? (7)
I believe the answer is:
satanic
'black?' is the definition.
(thesaurus)
'pocketing a brown so' is the wordplay.
'pocketing' indicates putting letters inside (pocket can mean to steal or take possession of).
'brown' becomes 'tan' (tan is a kind of brown).
'so' becomes 'sic' ('so' in Latin).
'a'+'tan'='atan'
'atan' going into 'sic' is 'SATANIC'.
'coming to' acts as a link.
(Other definitions for satanic that I've seen before include "Fiendish" , "wicked" , "Like the Devil" , "Like hell it is" , "Bad" .)