Spots all cheetahs need evidently, first of all (4)
I believe the answer is:
acne
'spots' is the definition.
(I've seen this before)
'all cheetahs need evidently first of all' is the wordplay.
'first of all' suggests taking the first letters.
The initial letters of 'all cheetahs need evidently' is 'ACNE'.
(Other definitions for acne that I've seen before include "Skin problem, mainly of teenagers" , "Facial spots" , "Skin condition associated with pimples" , "Skin affliction" , "Adolescent skin disease" .)