Yobs lashing out about nothing repeatedly (9)
I believe the answer is:
hooligans
'yobs' is the definition.
('hooligan' can be a synonym of 'yob')
'lashing out about nothing repeatedly' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'about' is an insertion indicator.
'nothing' becomes 'o' (looks like zero - 0).
'repeatedly' says to double the letters.
'lashing' anagrammed gives 'hligans'.
'o' duplicated is 'oo'.
'hligans' placed around 'oo' is 'HOOLIGANS'.
(Other definitions for hooligans that I've seen before include "Thugs" , "Violent troublemakers" , "delinquents" , "More than one tough" , "football louts" .)