Group with intelligence probing what follows fa or do (6)
I believe the answer is:
social
'do' is the definition.
(I've seen this before)
'group with intelligence probing what follows fa' is the wordplay.
I cannot quite see how this works, but
'intelligence' could be 'cia' (Central Intelligence Agency) and 'cia' is found in the answer.
'fa' could be 'o' (short for Fanny Adams, meaning nothing or 0) and 'o' is present in the answer.
This explanation may well be incorrect...
'or' acts as a link.
Can you help me to learn more?
(Other definitions for social that I've seen before include "Sort of security" , "Gregarious or neighbourly" , "Of people; gathering" , "Of society or its organisation" , "Convivial - party" .)