We've all been told to 'focus' at some point along the way. No one ever really defines what that means beyond "pay attention to what I need you to see". Focus seems to be a fleeting thing, a temporary sharpening, an unsustainable reaction for the average person. For most, focus = concentration and that's not the same thing.
In terms of career, most of us don't have a focus beyond (perhaps) subject matter expertise. We have an area of interest or an industry for which we were/are trained.
In the past decade, numerous books and gurus have talked about focus in terms of finding one's passion or a calling. Unfortunately, the cares of life can make some necessary demands and pull our focus from even a 'calling'. As a theatre artist working in IT management, my focus is pulled from writing even as I use my directing and production skills. My passion to teach and build community becomes a backseat driver to the requirements of building a unified team across a large company.
I'm not sure how to answer or define the question of focus. I believe that we need subject matter experts and generalists. I believe we need to understand our own drivers and dreams and never abandon them - but that paying rent and buying food may create detours.
I am left playing with the following:
Focus = Passion
Focus = Goal
Focus = Self-awareness
Focus = Happens when you need to take a step forward
Focus is not what others demand of you on their behalf but what you offer of yourself from your desire.