Part of circle succeeded -- still surviving (7)

I believe the answer is:

sextant

'part of circle' is the definition.
(mathematical term)

'succeeded still surviving' is the wordplay.
'succeeded' becomes 's' (genealogical abbreviation).
'still surviving' becomes 'extant' (I've seen this before).
's'+'extant'='SEXTANT'

(Other definitions for sextant that I've seen before include "Navigator's instrument" , "Navigational aid" , "Astronavigation instrument" , "Mariner's instrument" , "Sighting instrument" .)

I've seen this clue in The Telegraph.

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