Tread (4)
'tread' is the definition.
(I know that tread can be written as step)
This is all the clue.
(Other definitions for step that I've seen before include "Ladder rung; pace" , "Prefix meaning related by remarriage" , "Set foot down on pest" , "Bit of mashed potato maybe" , "Footprint" .)
(Other definitions for pace that I've seen before include "Stride" , "Speed of a single step?" , "Gait" , "With the leave of; speed" , "Rate of progress" .)