Decent American backing Iraq's first plan (8)
I believe the answer is:
suitable
'decent' is the definition.
(thesaurus)
'american backing iraq's first plan' is the wordplay.
'american' becomes 'us'.
'backing' shows that the letters should be reversed in order.
'first' suggests taking the first letters.
'plan' becomes 'table' (I've seen this in other clues**).
The first letter of 'iraq' is 'i'.
'us' backwards is 'su'.
'su'+'i'+'table'='SUITABLE'
(Other definitions for suitable that I've seen before include "Becoming" , "In keeping" , "qualified" , "Appropriate, fitting" , "Right or appropriate" .)