Politicians love blocking judges (6)
I believe the answer is:
tories
'politicians' is the definition.
(I've seen this in other clues)
'love blocking judges' is the wordplay.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'blocking' is an insertion indicator.
'judges' becomes 'tries' (trying is a kind of judging).
'o' placed into 'tries' is 'TORIES'.
(Other definitions for tories that I've seen before include "Members of the English Conservative Party" , "Old British Conservatives" , "they're right" , "Members of the British Conservative Party" , "Sortie (anag.)" .)