Final is not altogether difficult -- I'm at ease (8)

I believe the answer is:

ultimate

'final' is the definition.
('ultimate' can be similar in meaning to 'final')

'not altogether difficult i'm at ease' is the wordplay.
'not altogether' indicates the answer is hidden within the clue.
'ULTIMATE' is hidden within 'difficult im at ease'.

'is' is the link.

(Other definitions for ultimate that I've seen before include "Last or final in a series or process" , "Final - mutilate (anag)" , "Happening last" , "Final or absolute" , "something extreme" .)

I've seen this clue in The Telegraph.

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