Washing receptacle (7)
(Other definitions for bathtub that I've seen before include "Where to soak (mainly US)" , "Vessel in which one washes oneself" , "Vessel for ablutions" , "Large container for washing" , "place to immerse the body" .)
(Other definitions for bath that I've seen before include "English spa city on the River Avon" , "SW spa city" , "City where Persuasion ends" , "Water container for washing" , "(Container for) ablution" .)