Revolutionary losing heart gets to falter (4)
I believe the answer is:
reel
'to falter' is the definition.
(thesaurus)
'revolutionary losing heart' is the wordplay.
'revolutionary' becomes 'rebel' (rebel is a kind of revolutionary).
'losing heart' suggests removing the centre.
'rebel' with its middle taken out is 'REEL'.
'gets' acts as a link.
(Other definitions for reel that I've seen before include "Cylinder on which something is wound" , "spin" , "Revolving spool" , "Stagger about in lively dance" , "Highland dance" .)