Regularly treat one unspecified condition (6)

I believe the answer is:

tetany

'condition' is the definition.
(I know that tetany is a condition)

'regularly treat one unspecified' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'one unspecified' becomes 'any' (any example of something).
The alternate letters of 'treat' are 'tet'.
'tet'+'any'='TETANY'

(Another definition for tetany that I've seen is " nervy state".)

I've seen this clue in The Times.

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