$tag = wp_get_post_tags($post->ID);

Array
(
   [0] => stdClass Object
       (
           [term_id] => 4
           [name] => tag2
           [slug] => tag2
           [term_group] => 0
           [term_taxonomy_id] => 4
           [taxonomy] => post_tag
           [description] =>
           [parent] => 0
           [count] => 7
       )

   [1] => stdClass Object
       (
           [term_id] => 7
           [name] => tag5
           [slug] => tag5
           [term_group] => 0
           [term_taxonomy_id] => 7
           [taxonomy] => post_tag
           [description] =>
           [parent] => 0
           [count] => 6
       )

)

$tag[0]['slug']

$tag[0]->slug