What does the cryptic crossword clue "Monkey rushes out of its tree? (6)" mean?

The definition is "Monkey". The wordplay uses an anagram. anagram of RUSHES = RHESUS; definition: "Monkey" The answer is Rhesus.

Monkey rushes out of its tree? (6)

Telegraph Prize Cryptic #3110 | 9 Across | 2021-05-30 flower