Cheap flat (9)
I believe the answer is:
tasteless
I believe this is a double definition.
'cheap' is the first definition.
('tasteless' can be similar in meaning to 'cheap')
'flat' is the second definition.
('tasteless' can be similar in meaning to 'flat')
(Other definitions for tasteless that I've seen before include "Lacking flavour or aesthetic appreciation" , "Vapid" , "Insipid - vulgar" , "Lacking in aesthetic judgement" , "Lacking flavour or ability to appreciate the beautiful" .)