Telemachus is a young man with very little experience compared to the actual protagonist, Odysseus. Telemachus has never left his hometown, and yet, due to his father Odysseus being away fighting a war, a group of suitors has taken up residence in his home, and are all vying for his mother, Penelope.
The Innocent as an archetype is a character that has bad things forced upon them by pure chance or external forces. Telemachus is an average man, yet believes his father is dead and is stuck in a home with multiple scummy suitors.
Telemachus, really, has done nothing wrong and is still experiencing incredibly hard times for seemingly no reason, making him an example of the Innocent archetype.