Single doctor in US city, one opposing local development (5)
I believe the answer is:
nimby
'one opposing local development' is the definition.
(abbreviation for 'not in my back yard')
'single doctor in us city' is the wordplay.
'single' becomes 'i' (one).
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus**).
'in' means one lot of letters goes inside another.
'us city' becomes 'ny' (I've seen this in other clues).
'i'+'mb'='imb'
'imb' going inside 'ny' is 'NIMBY'.
(Other definitions for nimby that I've seen before include "One wanting to protect area" , "I don't want it near where I live" , "One objecting to local developments" , "Someone who objects to something being sited in their own locality" , "Self-interested objector to local development" .)