Clean as a Perth outhouse (6)
I believe the answer is:
washed
'clean' is the definition.
(similar in meaning)
'a perth outhouse' is the wordplay.
'a perth' becomes 'wa' (I can't explain this - if you can you should give a lot more credence to this answer).
'outhouse' becomes 'shed' (I've seen this before).
'wa'+'shed'='WASHED'
'as' is the link.
Can you help me to learn more?
(Other definitions for washed that I've seen before include "free of sin" , "Cleaned with liquid" , "Used soap and water" , "Cleaned with water" , "Laundered" .)