This is a hard play to read and one of the most difficult plays to translate from the Greek into English. In order to understand these words, you need to know the context a little.
The goddess Artemis punished Agamemnon for killing a deer in her sacred grove. The punishment was that there was no wind to allow the ships to sail to Troy. Calchis, the seer, told Agamemnon that he needed to sacrifice his daughter, Iphigenia, to make atonement. So, he did. As you can imagine, Agamemnon's wife, Clytemnestra was filled with wrath and plotted his demise.
What makes Clytemnestra frightening is that she professed her love and took in Agamemnon only to slay him. She also took another lover, Aegisthus, Agamemnon's cousin. After the death of Agamemnon, they took control over the city.
In light of these points, the lioness is Clytemestra and the wolf is Aegisthus.