Prevent containers turning over (4)
I believe the answer is:
stop
'prevent' is the definition.
(stopping is a kind of preventing)
'containers turning over' is the wordplay.
'containers' becomes 'pots' (pot is a kind of container).
'turning over' is a reversal indicator.
'pots' written backwards gives 'STOP'.
(Other definitions for stop that I've seen before include "Pause - prevent" , "Check" , "cut out" , "Block; end; group of organ pipes" , "Plug - organ knob - bus halt - period" .)