You are interviewing someone outside and you found a perfect spot, your head room, nose room EVERYTHING is great! You give your shot another look and realize that it appears as though there is a tree growing out of your subject's head! UGH!
Nope, you are not going to fix it in post. That would be hours of work to probably end up creating a fix that doesn't look too great.
So, you have to move your subject and recompose. It's important to look at all of these things before you shoot. Consider all possibilities with regard to framing. Don't be afraid to take some time, and not go with the easiest most obvious shot.
Or you can work with depth of field (keep the background blurry)