The breakfast I ordered hasn't arrived yet. Please bring it right away.
Literal
Order-[state-てある] breakfast [subject-が] still come-not. Right-away bring-please.
~てある expresses a resultant state from a deliberate action — '[the breakfast] has been ordered (and remains in that state).' Distinct from ~ている, which describes an ongoing action or a spontaneous resultant state. 頼んである朝食 = 'breakfast that has been (deliberately) ordered.' 持ってくる ('bring') = 持つ ('hold') + くる ('come').