Long-horned grasshopper (7)
I believe the answer is:
katydid
'long-horned grasshopper' is the definition.
(katydid is a kind of long-horned grasshopper)
This is all the clue.
(Other definitions for katydid that I've seen before include "Large cricket" , "American grasshopper" , "insect" , "American bush cricket" , "US bush cricket" .)