Pest visibly envious and cunning (8)
I believe the answer is:
greenfly
'pest' is the definition.
(I've seen this before)
'visibly envious and cunning' is the wordplay.
'visibly envious' becomes 'green' (I am not sure about the 'visibly' bit.).
'and' says to put letters next to each other.
'cunning' becomes 'fly' (fly can mean skilful or sharp).
'green'+'fly'='GREENFLY'
Can you help me to learn more?
(Other definitions for greenfly that I've seen before include "Common aphid" , "Common aphids" , "Garden pest" , "Pests" .)