Heads of select European judiciary meeting Polish assembly (4)
I believe the answer is:
sejm
'polish assembly' is the definition.
(I've seen this in another clue)
'heads of select european judiciary meeting' is the wordplay.
'heads of' suggests taking the first letters.
The first letters of 'select european judiciary meeting' is 'SEJM'.
(Other definitions for sejm that I've seen before include "European parliament" , "Polish house" .)