Either side of washroom being covered in dirt (4)
I believe the answer is:
worm
'dirt' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'either side of washroom being covered' is the wordplay.
'either' becomes 'or' (I've seen this in another clue).
'side of' suggests removing the centre (I've seen 'sides of' mean this (only the letters on the sides remain)).
'being covered' is an insertion indicator.
'washroom' with its centre taken out is 'wm'.
'or' inserted within 'wm' is 'WORM'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for worm that I've seen before include "Wriggle" , "one leaving cast" , "Vermiform wriggler" , "Squirm" , "Creeping invertebrate" .)