"an agreed" is correct and usable in written English.
You can use it when referring to an agreement that two or more parties have come to. For example, "We reached an agreed upon price for the vehicle."
An appointment is made at an agreed time to undergo assessment.
These competing interests among nations need to be replaced with an agreed-upon international system to harmonize existing rules within an agreed upon framework of law.
They also lack an agreed successor.
Like an agreed international glossary!
There is an agreed strategy".
All coauthors must sign an agreed wording.
"This an agreed-upon sale".
Following an agreed-upon methodology can promote a thorough, disciplined, and rigorous board oversight process.
Mediation is a negotiation between two or more parties facilitated by an agreed-upon third party.
A negotiation between two or more parties facilitated by an agreed-upon third party.
Despite an increasingly complex academic discourse, the videogame medium lacks an agreed-upon definition.
