1. think or act in a clever, sensible way
he seems to have his head on straight
If you say that someone 'has their head screwed on' or 'has their head screwed on straight', you usually mean that they have common sense or behave in a sensible or practical way. This is a casual expression, but it is often used in both social and professional contexts to talk about someone who is capable or who makes good decisions. Similar in meaning to 'being switched on' or 'having a good head on your shoulders'.