One of a troop rushes about (6)
I believe the answer is:
rhesus
'one of a troop' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'rushes about' is the wordplay.
'about' indicates an anagram.
'rushes' with letters rearranged gives 'RHESUS'.
Can you help me to learn more?
(Other definitions for rhesus that I've seen before include "The Rh in "Rh factor"" , "Small, long-tailed monkey" , "Often a positive factor in man" , "King, in Greek mythology" , "Asian monkey - blood factor" .)