Left to one side of shelf (5)
I believe the answer is:
ledge
'shelf' is the definition.
(I know that shelf can be written as ledge)
'left to one side' is the wordplay.
'left' becomes 'l' (common abbreviation).
'to one side' becomes 'edge' (edge is a kind of side).
'l'+'edge'='LEDGE'
'of' acts as a link.
(Other definitions for ledge that I've seen before include "A step" , "Rock shelf" , "Ability to contain one's emotions" , "Projecting ridge on a mountain" , "Ridge or shelf" .)