Ever need to add an excerpt field for WordPress when working with pages? There is an easy, one line way to do this (no plugin needed). Simply add this to your theme’s functions.php file:
add_post_type_support( 'page', 'excerpt' );
Once you have that in place – you can then use the WordPress the_excerpt() function to show the excerpt within the theme.
Here is another great way to get post and page excerpts on your wordpress site http://addall.in/reference/get-the-page-excerpt-wordpress