Uproar from the right after bill incorporates small addition (9)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

NOISE (uproar) reversed (from the right = reading right to left), after ACC (abbreviation for account = bill), containing S (abbreviation for small). In the sense of a country’s accession (addition) to a grouping such as NATO or the EU.