Former European politician in split that's unplanned (9)

I believe the answer is:

extempore

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'unplanned' is the definition.
Both the answer and definition are adjectives. Perhaps there's an association between them I don't understand?

'former european politician in split' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'european' becomes 'E' (abbreviation e.g. EU).
'politician' becomes 'MP' (Member of Parliament).
'in' is an insertion indicator.
'split' becomes 'tore' (I've seen this in another clue).
'e'+'mp'='emp'
'emp' put inside 'tore' is 'tempore'.
'ex'+'tempore'='EXTEMPORE'

'that's' is the link.

Can you help me to learn more?

(Other definitions for extempore that I've seen before include "Ad lib" , "Off-the-cuff" , "on the spot" , "offhand" , "Dashed off" .)

I've seen this clue in The Telegraph.

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