Means of checking rules, we're told (5)
I believe the answer is:
reins
'means of checking' is the definition.
(I've seen this before)
'rules we're told' is the wordplay.
'rules' becomes 'reigns' (reign can mean to rule or govern).
'we're told' indicates a 'sounds like' (homophone) clue.
'reigns' is a homophone of 'REINS'.
(Other definitions for reins that I've seen before include "Guiding straps" , "Means of control for a horse" , "Straps to control" , "Means of controlling a horse" , "Horse's controls" .)