Glaringly obvious, in retrospect - expelling extreme elements of Labour (5)

I believe the answer is:

natal

'of labour' is the definition.
(relating to childbirth or labour)

I can't explain the remainder of the clue.

(Other definitions for natal that I've seen before include "of an ass?" , "former SA province" , "Province at one time" , "Brazilian port" , "KwaZulu-____ , South African province" .)

I've seen this clue in The Independent.

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