Something like this should work:
.anvil-component.radio {
display: flex; /* optional - affects the alignment of the radio btn */
}
.anvil-component.radio label {
display: flex;
align-items: center;
flex-direction: column;
}
.anvil-component.radio input[type="radio"] {
position: relative;
}
This assumes you want this bevaiour for all radio buttons
You could add a role and prefix the above css with .anvil-role-myrole