Cover-up somewhat ticks off one of those in The House (5)

I believe the answer is:

attic

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'in the house' is the definition.
('attic' is part of 'house')

'cover-up somewhat ticks off one of those' is the wordplay.
'ATTIC' is hidden in amongst the letters.
However, I am unsure how this is indicated.

Can you help me to learn more?

(Other definitions for attic that I've seen before include "The highest room" , "Top storey" , "Upper chamber" , "Top apartment" , "from Greece" .)

I've seen this clue in The Irish Times and the Irish Times (Crosaire).

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