Pedometer unit (4)
I believe the answer is:
step
'pedometer unit' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for step that I've seen before include "Prefix meaning related by remarriage" , "Pace - part of a procedure" , "Footprint" , "Stair" , "Rung, dance movement" .)