Is round about? Yes, really (3)
I believe the answer is:
sic
'yes really' is the definition.
(shows an error has been quoted word-for-word)
'is round about?' is the wordplay.
'round' says the letters should be written backwards.
'about?' becomes 'c' (abbreviation for 'circa').
'is' reversed gives 'si'.
'si'+'c'='SIC'
(Other definitions for sic that I've seen before include "poorly spelt if requiring this" , "Thus in classical way" , "Like" , "the reading is correct" , "Intentionally so written" .)