Blunder in good French stereo centre (5)
I believe the answer is:
boner
'blunder' is the definition.
(I know that blunder can be written as boner)
'good french stereo centre' is the wordplay.
'good french' becomes 'bon' ('good' in French).
'centre' indicates the central letters.
The centre of 'stereo' is 'er'.
'bon'+'er'='BONER'
'in' acts as a link.
(Other definitions for boner that I've seen before include "butcher?" , "Stupid mistake" .)