Endures, though finishing at one's wits' end (5)
I believe the answer is:
lasts
'endures' is the definition.
('last' can be a synonym of 'endure')
'at one's wits' end' is the wordplay.
'at' is a charade indicator (letters next to each other).
'one's wits'' becomes 's' (I can't explain this - if you can you should give a lot more credence to this answer).
'end' becomes 'last' (I've seen this before).
's' after 'last' is 'LASTS'.
'though finishing' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for lasts that I've seen before include "Keeps on" , "Endures" , "Goes on" , "Holds out" , "carries on" .)