Carry on to the end (4)
I believe the answer is:
last
This clue is a double definition.
'carry on' is the first definition.
(thesaurus)
'the end' is the second definition.
(thesaurus)
'to' acts as a link.
(Other definitions for last that I've seen before include "Bringing up the rear" , "Most unlikely" , "Least likely" , "` `Let the cobbler stick to his ....' '" , "Continue" .)