Open above letter (5)

I believe the answer is:

overt

'open' is the definition.
(I know that open can be written as overt)

'above letter' is the wordplay.
'above' becomes 'over' (I've seen this before).
'letter' becomes 't' ().
'over'+'t'='OVERT'

(Other definitions for overt that I've seen before include "Done in an obvious way" , "Voter (anag.)" , "Open to view" , "Not concealed - public" , "Obvious, patent" .)

I've seen this clue in The Irish News.

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