Reduce speed (4)
'reduce speed' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for slow that I've seen before include "Dull-witted - late" , "lacking any precipitation" , "Not getting a move on" , "Moving at low speed" , "Dilatory" .)
'reduce speed' is the definition.
(I've seen this before)
This is all the clue.
(Another definition for slow up that I've seen is " Start to stop".)