Servant fetches doctor in the city (6)
I believe the answer is:
'city' is the definition.
(Madrid is an example)
'servant fetches doctor' is the wordplay.
I cannot really see how this works, but
'doctor' could be 'dr' (abbreviation) and 'dr' is located in the answer.
'servant' could be 'maid' (maid is a kind of servant) and 'maid' is present in the leftover letters.
No letters remain.
This may be the basis of clue (or it may be nonsense).
'in the' acts as a link.
Can you help me to learn more?
(Other definitions for madrid that I've seen before include "Spanish city" , "Spain's capital" , "Spanish capital" , "European capital city" , "Capital of Spain since 1561" .)