Removed covers one never ultimately used (9)
I believe the answer is:
exercised
'used' is the definition.
(exercising is a kind of using)
'removed covers one never ultimately' is the wordplay.
'removed' becomes 'excised' (I've seen this before).
'covers' means one lot of letters goes inside another.
'ultimately' says to take the final letters.
The final letters of 'one never' are 'er'.
'excised' going around 'er' is 'EXERCISED'.
(Other definitions for exercised that I've seen before include "Worked out" , "Practised" , "worried" , "Kept fit" .)