Artwork flipping rubbish, which may be a minus (8)
I believe the answer is:
operator
'which may be a minus' is the definition.
(I know that minus sign is a operator)
'artwork flipping rubbish' is the wordplay.
'artwork' becomes 'opera' (opera is a type of artwork).
'flipping' is a reversal indicator.
'rubbish' becomes 'rot' (both can mean nonsense).
'rot' backwards is 'tor'.
'opera'+'tor'='OPERATOR'
(Other definitions for operator that I've seen before include "Manipulator" , "Director or controlller of machinery" , "Manipulative type of person" , "Agent that runs some apparatus or machine" , "Wheeler-dealer - telephonist" .)