People with this complaint may easily be spotted (7)
I believe the answer is:
measles
'people with this complaint may easily be spotted' is the definition.
'measles' can be an answer for 'complaint' (measles is a kind of health problem). I am not certain of the rest of the definition.
This is all the clue.
Can you help me to learn more?
(Other definitions for measles that I've seen before include "Infectious disease covering body with red spots" , "Disease where spots may be seen" , "Disease suffered in childhood" , "Viral disease with rash" , "Childhood viral disease" .)