Round spots don't start or finish (4)
I believe the answer is:
stop
'finish' is the definition.
(I know that finish can be written as stop)
'round spots don't start' is the wordplay.
'round' shows that the letters should be reversed in order.
'don't start' means to remove the first letter.
'spots' with its first letter taken away is 'pots'.
'pots' written backwards gives 'STOP'.
'or' acts as a link.
(Other definitions for stop that I've seen before include "Withhold payment" , "Standstill" , "Finished" , "Organ knob; get bus here" , "Plug; cease" .)