Specialist unchanged, showing slight concave outline (7)

I believe the answer is:

entasis

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'slight concave outline' is the definition.
The definition suggests a singular noun which matches the answer.

'specialist unchanged' is the wordplay.
'specialist' becomes 'ent' (Ear, Nose and Throat specialist).
'unchanged' becomes 'as is' (I've seen this in another clue).
'ent'+'asis'='ENTASIS'

'showing' is the link.

Can you help me to learn more?

(Other definitions for entasis that I've seen before include "Shaping of a column for optical effect" , "Convex curve of a column shaft" , "Curvature of column" , "Shape of columns" , "slightly convex shape" .)

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

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