Posh patio relaid in perfect place (6)
I believe the answer is:
utopia
'perfect place' is the definition.
(an imagined perfect place)
'posh patio relaid in' is the wordplay.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-U).
'relaid' is an anagram indicator (letters laid again).
'in' indicates putting letters inside.
'patio' is an anagram of 'topia'.
'u' inserted into 'topia' is 'UTOPIA'.
(Other definitions for utopia that I've seen before include "Perfect, yet impracticable, state" , "Thomas More's favourite place" , "Thomas More's ideal state" , "Heaven" , "Sir Thomas More's ideal society" .)