You need to license the clip each time you sell the ad to a different customer.
Enhanced licenses means that you selected Premium content. Premium content has different license rules. Extended licenses are NOT available for premium content.
Look here for more information on licensing: https://community.adobe.com/t5/stock/links-for-licensing-terms/td-p/11366788
(Disclaimer: As always with licensing, this is my interpretation of the rules. I think they are correct and advice is based reading and interpreting the license terms and on fair use for both the buyer and the artist/stock company, but I can not rule out that my interpretation is wrong. I'm not an Adobe employee)
ABAMBO | Hard- and Software Engineer | Photographer