A FAA diz (por 14 CFR 91.185):
If the clearance limit is not a fix from which an approach begins, leave the clearance limit at the expect-further-clearance time if one has been received, or if none has been received, upon arrival over the clearance limit, and proceed to a fix from which an approach begins and commence descent or descent and approach as close as possible to the estimated time of arrival as calculated from the filed or amended (with ATC) estimated time en route.
Isso parece responder à sua pergunta, a menos que você tenha uma pergunta mais específica. Você pode descer para um IAF como achar melhor e iniciar qualquer abordagem. ATC irá limpar o caminho.