Quite severe in nature, regularly... (7)

I believe the answer is:

austere

I'm a little stuck... Click here to teach me more about this clue!

'quite severe in nature regularly' is the definition.
I can't tell whether this definition defines the answer.

'severe in nature regularly' is the wordplay.
'severe' becomes 'ster' (I can't justify this - if you can you should give a lot more credence to this answer).
'in' is an insertion indicator.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternating letters of 'nature' are 'aue'.
'ster' going within 'aue' is 'AUSTERE'.

Can you help me to learn more?

(Other definitions for austere that I've seen before include "Severe or strict in attitude" , "Severe, ascetic" , "Bleak" , "not of luxury type" , "Abstemious and grave" .)

I've seen this clue in the Sydney Morning Herald.

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