Prevent containers being brought up (4)
I believe the answer is:
stop
'prevent' is the definition.
(I know that block is a is a more specific form of the action of stop)
'containers being brought up' is the wordplay.
'containers' becomes 'pots' (pot is a kind of container).
'being brought up' is a reversal indicator (in a down clue, letters go up).
'pots' in reverse letter order is 'STOP'.
(Other definitions for stop that I've seen before include "Plug - organ knob - bus halt - period" , "Plug; cease" , "Pause - prevent" , "Close < finish" , "Arrest" .)