Cleaner, Flash, regularly put on lavatory (6)
I believe the answer is:
loofah
'cleaner' is the definition.
(I've seen this before)
'flash regularly put on lavatory' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'put on' says to put letters next to each other.
'lavatory' becomes 'loo' (loo is a kind of lavatory).
The alternate letters of 'flash' are 'fah'.
'fah' after 'loo' is 'LOOFAH'.
(Other definitions for loofah that I've seen before include "Flesh brush" , "Rough sort of sponge" , "Bathtime accessory" , "Bathroom sponge made of halo" , "Dried gourd pod used as bath sponge" .)