Arboreal primate (5)
'arboreal primate' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for lemur that I've seen before include "Ring-tailed prosimian" , "Monkey-like aniaml of Madagascar" , "Nocturnal primate from Madagascar" , "one in the bush?" , "Long-tailed primate" .)
(Other definitions for orang that I've seen before include "Short tree-dweller" , "Forest-dweller with red hair" , "Large ape" , "Wild animal briefly appeared" , "- - -utan" .)
(Other definitions for spider monkey that I've seen before include "Rainforest dweller" , "Long-limbed simian" , "primate" , "climber" .)