Surprised comment about label that’s brought back name of detective writer (6)
I believe the answer is:
agatha
'name of detective writer' is the definition.
(Agatha Christie)
'surprised comment about label that's brought back' is the wordplay.
'surprised comment' becomes 'aha' (expression of surprise).
'about' is an insertion indicator.
'label' becomes 'tag' (tag is a kind of label).
'that's brought back' is a reversal indicator.
'aha' enclosing 'tag' is 'ahtaga'.
'ahtaga' back-to-front is 'AGATHA'.
(Other definitions for agatha that I've seen before include "Detective story writer" , "female" , "- Christie, twentieth century crime novelist" , "Girl" , "-- Christie, English novelist" .)