eisiau is a noun meaning 'a need, a want'. While eisiau can be used for either English word, the word angen is also commonly used for 'a need'.
In this particular sentence, though, the English phrase 'There is no need...' is more usual in the context than 'There is no want...'
That is because the usual meaning of mynd is 'going, to go', and so we generally stick with that.
We cannot cover every meaning of all the words introduced in Duo. Many words have wider or less common meanings depending on their context, and these can be found in a dictionary or thesaurus.