The TiddlyWiki.prototype.getTiddlerText supports accessing sections in a tiddler.

If a tiddler has a heading (!Heading) in the markup of its text anything that follows that heading is returned.

For example given a tiddler with title "Title" which has the following text:
!Heading
foo
A call to
store.getTiddlerText|("Title##Heading")
will return "foo"
bag
tiddlywikidev_public
created
Wed, 02 Nov 2011 10:47:29 GMT
creator
jon
modified
Wed, 02 Nov 2011 10:47:29 GMT
modifier
jon
tags
transclusion