To some extent, Blunkett etc on about group (7)
I believe the answer is:
octette
'group' is the definition.
(octette is a kind of group)
'to some extent blunkett etc on about' is the wordplay.
'to some extent' indicates a hidden word.
'about' says the letters should be written in reverse.
'ettetco' is hidden within 'blunkett etc on'.
'ettetco' in reverse letter order is 'OCTETTE'.
(Other definitions for octette that I've seen before include "Eight musicians" , "Noted work" , "Group of eight" .)