Inexperienced with cunning garden pests (8)
I believe the answer is:
greenfly
'garden pests' is the definition.
'greenfly' can be an answer for 'pests' (I've seen this before). I am not sure about the 'garden' bit.
'inexperienced with cunning' is the wordplay.
'inexperienced' becomes 'green' (similar in meaning).
'with' 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 "Garden pest" , "Common aphid" , "Pests" , "Common aphids" .)