Shelters not opened in these pleasant garden spots (7)

I believe the answer is:

arbours

'these pleasant garden spots' is the definition.
(shaded garden areas)

'shelters not opened' is the wordplay.
'shelters' becomes 'harbours' (harbouring is a kind of sheltering).
'not opened' means to remove the first letter.
'harbours' with its first letter taken away is 'ARBOURS'.

'in' acts as a link.

(Another definition for arbours that I've seen is " Frameworks supporting climbing plants".)

I've seen this clue in The Telegraph.

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