Flat entrance partly concealed (6)

I believe the answer is:

latent

'concealed' is the definition.
(thesaurus)

'flat entrance partly' is the wordplay.
'partly' indicates a hidden word.
'LATENT' is hidden within 'flat entrance'.

(Other definitions for latent that I've seen before include "Unrealised, potential" , "There but not yet effective" , "Potential not realised" , "Potential but not active" , "Existing but not yet active, say talent" .)

I've seen this clue in The Telegraph.

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