Doctor left note for spy (4)
I believe the answer is:
mole
'for spy' is the definition.
(mole is a kind of spy)
'doctor left note' is the wordplay.
I cannot quite understand how this works, but
'doctor' could be 'mo' (medical officer) and 'mo' is found in the answer.
'left' could be 'l' (common abbreviation) and 'l' is located in the answer.
'note' could be 'e' (musical note) and 'e' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for mole that I've seen before include "Spy, skin spot and furry animal" , "Spot - traitor" , "A spy within an organisation" , "Skin spot; breakwater" , "Tunneller" .)