Save buddypress xprofile data to author meta

Use this action hook found in buddypress/bp-xprofile/classes/class-bp-xprofile-profiledata.php

do_action_ref_array( 'xprofile_data_after_save', array( $this ) );

You’ll need to use the actual field_id for your xprofile description. This example assumes it is 25. You can get the field_idby going to wp-admin > Users > Profile Fields and clicking ‘Edit’ on that field. The field_id will appear in the browser url.

function echoashu_save_description( $obj ) {

    if ( $obj->field_id == 25 ) {
        update_user_meta( $obj->user_id, 'description', $obj->value );
    }
}
add_action( 'xprofile_data_after_save', 'echoashu_save_description' );