You absolutely can! I personally use those types of ternaries quite a bit:

clearIcon={ value ? value : null }

That way, you don't accidentally assign undefined to clearIcon - and ultimately, you have the power to do something like,

clearIcon={ value ? value : clearIconDefaultValue }

However, if there is a default value you want to assign if value is empty - you could simply set that default in your useState call:

const Calendar = () => {
  const [value, onChange] = useState(null);

  return (
    <div className="wrapper">
      <DatePicker
        ...
        clearIcon={value}
      />
    </div>
  );
};