[Sturm]

Save file in quests/global/items folder as:
script_1000.pl

sub EVENT_ITEM_CLICK {

   if ($itemid == 999999 && $ulevel <= 10 && !defined $qglobals{"Defiant10"}) {
        $client->NukeItem(999999);
		quest::setglobal("Defiant10", 1, 5, "F"); #prevent player from using item again
		quest::summonitem(123456); #whatever your defiant armor item ID is you want to add
		$client->Message(18, "You've summoned Defiant Armor!");
    } else {
        $client->Message(15, "Nice try, you're too powerful to use this.");
    }
}

Add the number of the script file to the item in the "Script File ID:" in this case it would be "1000". Add in any extra perl you want to suit your needs into the code and TADA! Item that uses a script on click.

Edit: I didn't check this for syntax or to see if it works, it should but just pointing you in the right direction here. Good luck!