A laundry is partly under water (5)
I believe the answer is:
awash
'partly under water' is the definition.
(I've seen this before)
'a laundry' is the wordplay.
'laundry' becomes 'wash' (synonyms).
'a'+'wash'='AWASH'
'is' acts as a link.
(Other definitions for awash that I've seen before include "With the top just covered with water" , "Flooded; about to sink" , "not quite under" , "Flood" , "Covered by water - sounds cleansing" .)