Controlled what monarch did, reportedly (6)
I believe the answer is:
reined
'controlled' is the definition.
(reining is a kind of controlling)
'what monarch did reportedly' is the wordplay.
'what monarch did' becomes 'reigned'.
'reportedly' indicates a 'sounds like' (homophone) clue.
'reigned' sounds like 'REINED'.
(Other definitions for reined that I've seen before include "Restrained" , "Pulled in, checked progress" , "Stopped or slowed a horse" .)