Stern about matter with Republican official (9)

I believe the answer is:

registrar

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'official' is the definition.
(I know that registrar is a type of official)

'stern about matter with republican' is the wordplay.
'stern' becomes 'rear' (rear of a ship).
'about' indicates putting letters inside.
'matter with' becomes 'gist' (I am not sure about the 'with' bit.).
'republican' becomes 'R' (abbreviation).
'gist'+'r'='gistr'
'rear' enclosing 'gistr' is 'REGISTRAR'.

Can you help me to learn more?

(Other definitions for registrar that I've seen before include "Official record keeper" , "Recorder of births, deaths and marriages" , "Official recorder" , "clerk" , "Medic" .)

I've seen this clue in The Telegraph.

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