Something said about a blemish (6)
I believe the answer is:
remark
'something said' is the definition.
(a comment or utterance)
'about a blemish' is the wordplay.
'about' becomes 're' (common abbreviation for 'with reference to').
'a blemish' becomes 'mark' (mark is a kind of blemish).
're'+'mark'='REMARK'
(Other definitions for remark that I've seen before include "Something said; take notice of" , "Written or spoken comment" , "Make mention of" , "Notice; happen to say" , "(E.g. Virgil's) pastoral poems" .)