No crop is damaged by this insect (8)
I believe the answer is:
scorpion
'this insect' is the definition.
(thesaurus)
'no crop is damaged' is the wordplay.
'damaged' is an anagram indicator.
'no'+'crop'+'is'='nocropis'
'nocropis' is an anagram of 'SCORPION'.
'by' is the link.
(Other definitions for scorpion that I've seen before include "Sting-tailed creature" , "Kind of spider with pincers and stinging tail" , "Stinger with a long tail" , "Poisonous creature" , "Poisonous arachnid" .)