كتب : Hatem Maher
Veteran Desmond Maringwa scored the winner six minutes after restart to condemn the Tunisian giants to a surprising loss.
The visitors were unlucky not to level the score after two shots from Amine Chermiti and Mohamed Nafkha were denied by the post.
Etoile need to overturn the deficit in the second-leg in Sousse if they are to avoid an unthinkable elimination from the preliminary stages.
Dynamos will be looking to cause an upset and reach the elite competition's group stage at Etoile's expense.
Etoile won their first Champions League title in 2007 after a 3-1 aggregate victory over five-time African champions Ahli.