Wash three foreign articles (7)
I believe the answer is:
launder
'wash' is the definition.
(I know that wash can be written as launder)
'three foreign articles' is the wordplay.
'three' becomes 'la' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'foreign articles' becomes 'under'.
'la'+'under'='LAUNDER'
Can you help me to learn more?
(Other definitions for launder that I've seen before include "Wash and iron clothes etc" , "clean habits" , "Wash, starch and iron" , "Led a run (anag)" , "Make illegal (money) legitimate" .)