Assuming it start()uses variables / function also defined in its parent anonymous function, the easiest way I can imagine is to create a variable outside of jQuery that you assigned. Then you can call it both inside jQuery and outside jQuery.
Note. The disadvantage of this is that you can only call it start();after the page has finished loading. If you try to call start();before this, it will cause console errors.
Here is an example ...
var start = null;
$(function(){
var exampleVariable = "hello world";
start = function() {
alert(exampleVariable);
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="button" onclick="start();" value="Call Function"/>
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