Pseudo American passing Slough (5)
I believe the answer is:
bogus
'pseudo' is the definition.
(thesaurus)
'american passing slough' is the wordplay.
I cannot really understand how this works, but
'american' could be 'us' (abbreviation for United States) and 'us' is found in the answer.
'slough' could be 'bog' (I've seen this before) and 'bog' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for bogus that I've seen before include "Sham, counterfeit" , "Sham, false" , "Fake, phoney" , "Mock" , "Scribbled drawing" .)