Flat ring used in the laundry (6)
I believe the answer is:
washer
'flat ring' is the definition.
(I've seen this before)
'the laundry' is the wordplay.
I cannot quite see how this works, but
'laundry' could be 'wash' (synonyms) and 'wash' is located in the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'used in' acts as a link.
Can you help me to learn more?
(Other definitions for washer that I've seen before include "Plumber's rubber ring" , "Ring under a nut" , "Laundry machine" , "Perhaps laundryman" , "Metal disc for hawser" .)