Co-operating group assembling Brexit, Labour or Conservative leaders (4)
I believe the answer is:
bloc
'co-operating group assembling' is the definition.
I can't tell whether this definition defines the answer.
'brexit labour or conservative leaders' is the wordplay.
'leaders' indicates taking the first letters.
The first letters of 'brexit labour or conservative' is 'BLOC'.
Can you help me to learn more?
(Other definitions for bloc that I've seen before include "Axis (political)" , "Group of allied nations" , "Combination of parties or countries" , "Association of countries" , "Alliance - coalition" .)