Left deserving a little of what to Pope is dangerous (8)
I believe the answer is:
learning
'a little of what to pope is dangerous' is the definition.
('a little learning is a dangerous thing' - Pope)
'left deserving' is the wordplay.
'left' becomes 'l' (common abbreviation).
'deserving' becomes 'earning' (I've seen this before).
'l'+'earning'='LEARNING'
(Other definitions for learning that I've seen before include "Aquiring skill or knowledge" , "Discovering, finding out" , "Cognitive process of acquiring skill or knowledge" , "Lore" , "Instruction" .)