The phrase "foremost concern" means the most important matter or priority at hand. It is something that is given top priority and all efforts are directed towards addressing it.
The protection of a child is of foremost concern if she or he is abused. (ylaw.ca)
Whether collage, relief, assemblage or mixed - media sculpture, her work is foremost concerned with its own process. (michaelrosenfeldart.com)
Her success is largely due to her exceptional marketing ability and through creating a team of professionals whose foremost concern is the needs of their clients. (rismedia.com)