Learn Russian: Заказчица просит сделать этот пояс побольше. - The client f is asking to make this belt a little bigger.

Adding the prefix по- to a comparative adjective softens it. While больше just means "bigger", побольше means "a little bit bigger" or "somewhat bigger". It makes the client's request sound more polite and less demanding.

Why use заказчица instead of клиентка for "client"?

While both mean "female client", заказчица comes from the word заказ (an order). It specifically refers to someone who commissions custom work or a service, like tailoring or altering a belt, whereas клиентка is a broader term for any customer.

Why do we use the imperfective просит alongside the perfective сделать?

We use the imperfective просит because the asking is an ongoing action in the present. However, she is asking for a single, completed result (the belt being altered), which is why the perfective infinitive сделать is used.

Why is этот пояс seemingly in the nominative case when it is the direct object?

It is actually in the accusative case! Because пояс (belt) is a masculine, inanimate noun, its accusative form is identical to its nominative form.