Spots a staff alpha stepping down (4)
I believe the answer is:
acne
'spots' is the definition.
(skin condition causing spots)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for acne that I've seen before include "Adolescent skin disease" , "Skin disorder" , "Skin problem, mainly of teenagers" , "sort of disease" , "(Inflammation causing) spots" .)