When we recite ziarat e ashura we say "Ya thara Allah…" meaning the blood of Allah. What do we mean when we recite this?
As we know Allah doesn’t have parents,children or any partner and is the only one?

Translation is very poor. Revenge for the sake of God. God is disobeyed and therefore as God’s lovers he is angry for the sake of God and revenges from sinners and oppressors for the sake of God.
The other meaning is that God will revenge his blood like the family of one who is killed would do for their loved one.