Primate with a long tail (6)
I believe the answer is:
monkey
'primate with a long tail' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for monkey that I've seen before include "See 10" , "Small primate" , "PS500 (sl.)" , "Mischievous child; primate" , "Any of various long-tailed primates" .)