Seeking a guide for 2 adults - June 16 - 3:00PM, pick up / drop off in Fira, tour of Akrotiri, 4 - 5 hrs., incl. Museums in Fira
You can hire a guide at the entrance.
When we visited Akrotiri last May, it was not very easy to get a tour guide at the entrance. Maybe it was just our bad luck that day. There were very few tour guides at the entrance. One approached us and asked us to join her group of about 10 people. However, when she told everyone she can only accept cash, everyone dropped out of the group except for me and my husband. If it was just the two of us, it would have been very expensive. She told us to wait while she tried to round up more people but she didn't have any takers, so we ended up going on our own. There is some signage although it's not very detailed. We still enjoyed our visit. Maybe other people had better luck getting a tour guide at the entrance but we did not.
Our airbnb host recommended a local guide. We already had plans and so did not have the opportunity to work with him, so cannot specifically recommend, but he does provide the service you are looking for: https://www.tripadvisor.com/Attraction_Review-g189433-d20247792-Reviews-Milan_Manojlovic-Santorini_Cyclades_South_Aegean.html.