Shower cap placed around heated bath (9)
I believe the answer is:
bespatter
'shower' is the definition.
(both can mean to cover in liquid)
'cap placed around heated bath' is the wordplay.
'cap' becomes 'better' (I've seen this before).
'placed around' means one lot of letters goes inside another.
'heated bath' becomes 'spa' (spa can mean a hot bath).
'better' placed around 'spa' is 'BESPATTER'.
(Other definitions for bespatter that I've seen before include "Make mess of" , "Spray with droplets" , "Defame" , "Dirty" .)