Checks showers for auditor (5)
I believe the answer is:
reins
'checks' is the definition.
(reining is a kind of checking)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for reins that I've seen before include "Means of controlling a horse" , "Straps for controlling a horse" , "Means of control for a horse" , "Bridle straps" , "Rider's straps" .)