Single one brought in without blemish (9)
I believe the answer is:
unmarried
'single' is the definition.
(similar in meaning)
'one brought in without blemish' is the wordplay.
'one' becomes 'i' (roman numeral).
'brought in' indicates putting letters inside.
'without blemish' becomes 'unmarred'.
'i' going into 'unmarred' is 'UNMARRIED'.
(Other definitions for unmarried that I've seen before include "Status of a bachelor" , "Not yet wed" , "Single in terms of partnership" .)