Taken from under mat? It isn't rash (10)

I believe the answer is:

dermatitis

'rash' is the definition.
(thesaurus)

'taken from under mat? it isn't' is the wordplay.
'taken from' indicates a hidden word.
'DERMATITIS' is hidden within 'under mat it isnt'.

(Other definitions for dermatitis that I've seen before include "Skin inflammation" , "Skin ailment" , "Skin trouble" , "Met diarist (anag.)" .)

I've seen this clue in The Telegraph.

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