Ruffian spilling oil on hag (8)
I believe the answer is:
hooligan
'ruffian' is the definition.
(I know that bully can be written as hooligan)
'spilling oil on hag' is the wordplay.
'spilling' indicates anagramming the letters.
'oil'+'on'+'hag'='oilonhag'
'oilonhag' is an anagram of 'HOOLIGAN'.
(Other definitions for hooligan that I've seen before include "Undesirable" , "A young ruffian" , "Tough" , "Antisocial rough" , "Young rough" .)