Tizen Developers

You may try the code below. 

elm_entry_select_all(ad->entry); //take an Evas_Object pointer in the appdata struct named entry.

Write the button callback code as below:

evas_object_smart_callback_add(btn, "clicked", btn_clicked_cb, ad);

Then in the callback use the elm_entry_select_none() function. The code is given below:
 

static void
btn_clicked_cb(void *data, Evas_Object *obj, void *event_info)
{
    appdata_s* ad = data;
    elm_entry_select_none(ad->entry);
}

Hope it'll work. Please mark this post as the Best to promote to others if it helps.