Roughing up lout is no answer (8)
I believe the answer is:
solution
'answer' is the definition.
('solution' can be a synonym of 'answer')
'roughing up lout is no' is the wordplay.
'roughing up' indicates anagramming the letters (I've seen this in other clues).
'lout'+'is'+'no'='loutisno'
'loutisno' with letters rearranged gives 'SOLUTION'.
(Other definitions for solution that I've seen before include "you get when not concentrating?" , "Puzzle's answer" , "A mixture of liquid substances is the answer" , "may involve a certain concentration" , "A mixture of liquids" .)