Boot out the leaders of the extremely xenophobic party espousing lawlessness (5)
I believe the answer is:
expel
'boot out' is the definition.
(synonyms)
'the leaders of the extremely xenophobic party espousing lawlessness' is the wordplay.
'the leaders of' suggests taking the first letters.
The first letters of 'extremely xenophobic party espousing lawlessness' is 'EXPEL'.
(Other definitions for expel that I've seen before include "Drive away" , "Get rid" , "Deport" , "Remove from membership" , "Drive out - dispossess" .)