Look into organised group intending to be obstructive (6-6)
I believe the answer is:
bloody-minded
'obstructive' is the definition.
'look into organised group intending' is the wordplay.
'look' becomes 'lo' (archaic term meaning 'look!').
'into' means one lot of letters goes inside another.
'organised group' becomes 'body' (I've seen this before).
'intending' becomes 'minded'.
'lo' placed inside 'body' is 'bloody'.
'bloody'+'minded'='BLOODY-MINDED'
'to be' acts as a link.
(Other definitions for bloody-minded that I've seen before include "Deliberately obstructive (informal)" , "Deliberately uncooperative" , "Aggressively difficult" .)