Insect set beagle test (4,6)
I believe the answer is:
stag beetle
'insect' is the definition.
(stag beetle is a kind of insect)
'set beagle test' is the wordplay.
'set' indicates an anagram (instruction to set the letters).
'beagle'+'test'='beagletest'
'beagletest' is an anagram of 'STAG-BEETLE'.
(Other definitions for stag beetle that I've seen before include "Insect with antler-like jaws" , "Six-footer" , "something some folk find creepy" , "Horny little creature" , "Large insect with branched mandibles" .)