English doctor left space for symbol (6)
I believe the answer is:
emblem
'symbol' is the definition.
(I've seen this before)
'english doctor left space' is the wordplay.
'english' becomes 'e' (abbreviation).
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'left' becomes 'l' (common abbreviation).
'space' becomes 'em' (in typography, a space as wide as a letter 'm').
'e'+'mb'+'l'+'em'='EMBLEM'
'for' is the link.
(Other definitions for emblem that I've seen before include "Symbol, representative device" , "Device, badge or symbol" , "Mark" , "Symbolic device or badge" , "Representative object" .)