Complaint coming from Isaac Newton (4)
I believe the answer is:
acne
'complaint' is the definition.
(acne is a kind of disease)
'coming from isaac newton' is the wordplay.
'coming from' indicates a hidden word.
'ACNE' is hidden in the letters of 'isaac newton'.
(Other definitions for acne that I've seen before include "Skin spots" , "Facial spots" , "Adolescent skin disease" , "Spotty skin condition" , "Skin condition prevalent among teenagers" .)