Check balance, then shower (8)
I believe the answer is:
restrain
'check' is the definition.
(I know that check is a more specific form of the action restrain)
'balance then shower' is the wordplay.
'balance' becomes 'rest' (I've seen this before).
'then' says to put letters next to each other.
'shower' becomes 'rain' (synonyms).
'rest'+'rain'='RESTRAIN'
(Other definitions for restrain that I've seen before include "Control - check" , "bar" , "Tie up - arrest" , "Manacle" , "Keep back" .)