Not entirely frightful time in retreat (7)

I believe the answer is:

hideout

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'retreat' is the definition.
(I know that retreat can be written as hideout)

'not entirely frightful time in' is the wordplay.
'not entirely' means to remove the last letter (not all of the word).
'frightful' becomes 'hideous' (I've seen this before).
'time in' becomes 't' (abbreviation. I am not sure about the 'in' bit.).
'hideous' with its final letter taken away is 'hideou'.
'hideou'+'t'='HIDEOUT'

Can you help me to learn more?

(Other definitions for hideout that I've seen before include "Place to lie low" , "retreat" , "den" , "sanctuary" .)

I've seen this clue in The Times.

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