Some uncouth, ugly ruffian (4)
I believe the answer is:
thug
'ruffian' is the definition.
(thesaurus)
'some uncouth ugly' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'THUG' can be found hidden inside 'uncouth ugly'.
(Other definitions for thug that I've seen before include "Rough" , "Gorilla" , "Brutal criminal" , "16 21 [INDIAN IMPORT]" , "brute" .)