Amazed darn American rejected business (9)
I believe the answer is:
awestruck
'amazed' is the definition.
(thesaurus)
'darn american rejected business' is the wordplay.
'darn' becomes 'sew' (I've seen this in another clue).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'rejected' says the letters should be written in reverse.
'business' becomes 'truck' (dealings, as in 'having no truck with' something).
'sew'+'a'='sewa'
'sewa' back-to-front is 'awes'.
'awes'+'truck'='AWESTRUCK'
(Other definitions for awestruck that I've seen before include "Suck water (anag) - completely astonished" , "overcome by wonder" , "full of admiration" , "Wondering" , "Filled with amazement" .)