Check speaker’s shower (4)
I believe the answer is:
rein
'check' is the definition.
(both can mean to control or limit)
'speaker's shower' is the wordplay.
'speaker's' indicates a 'sounds like' (homophone) clue.
'shower' becomes 'rain' (synonyms).
'rain' sounds like 'REIN'.
(Other definitions for rein that I've seen before include "Strap on a bridle" , "Long strap to restrain" , "Curb" , "Hold back" , "A means of control" .)