One’s rewriting small features (5)
I believe the answer is:
noses
'features' is the definition.
(I have seen 'Facial features' mean 'noses' so perhaps 'features' could also mean 'noses')
'one's rewriting small' is the wordplay.
'rewriting' indicates an anagram.
'small' becomes 's' (abbreviation - e.g. clothes size**).
'ones' anagrammed gives 'nose'.
'nose'+'s'='NOSES'
(Other definitions for noses that I've seen before include "Hooters" , "Olfactory organs" , "Pries" , "Facial features" , "Proboscises" .)