Remove Republican gatecrashing facility (5)
I believe the answer is:
erase
'remove' is the definition.
(to erase is to remove)
'republican gatecrashing facility' is the wordplay.
'republican' becomes 'R' (abbreviation in US politics).
'gatecrashing' means one lot of letters goes inside another.
'facility' becomes 'ease' (facility can mean ease or absence of difficulty).
'r' going within 'ease' is 'ERASE'.
(Other definitions for erase that I've seen before include "Clear" , "Obliterate" , "Remove permanently" , "To remove all trace" , "Do away with" .)