Experimental subjects maybe steering equipment (8)
I believe the answer is:
controls
This clue is a double definition.
'experimental subjects' is the first definition.
(controls help to make experiments reliable)
'steering equipment' is the second definition.
(eg the controls of a vehicle)
'maybe' acts as a link.
(Other definitions for controls that I've seen before include "Directs or operates" , "Exercises power over" , "Regulates" , "Manages the regulatory mechanisms" , "Runs" .)