soluções do caso

gistfile1.php

    $query = DB::select('*')
       ->select(array(DB::expr('LEFT(`descricao`,10)'), 'descricao'))
       ->from('publics')
       ->limit(4)
       ->execute();

     ------------------------------------------------------------------

    public static function publics_slide()
    {
        $query = DB::select()
            ->from('publics')
            ->limit(4)
            ->execute();

        $result = array();

        if ($query)
        {
            foreach($query as $row)
            {
                $row['descricao'] = Str::truncate($row['descricao'], 10);
                $result[] = $row;
            }
        }
       
        return $result;  
    }