One observes no overturned dish? (8)
I believe the answer is:
onlooker
'one observes' is the definition.
(I've seen this before)
'no overturned dish?' is the wordplay.
'overturned' says the letters should be written in reverse.
'dish?' becomes 'looker' (I've seen this before).
'no' in reverse letter order is 'on'.
'on'+'looker'='ONLOOKER'
(Other definitions for onlooker that I've seen before include "Non-participant" , "He stands and watches" , "One who watches without becoming involved" , "Bystander" , "One observes" .)