Decent, extremely tidy real estate (8)
I believe the answer is:
property
'real estate' is the definition.
(I've seen this in another clue)
'decent extremely tidy' is the wordplay.
'decent' becomes 'proper' (synonyms).
'extremely' means to remove the middle letters (only the extremes of the word are used).
'tidy' with its middle removed is 'ty'.
'proper'+'ty'='PROPERTY'
(Other definitions for property that I've seen before include "Premises" , "Something owned" , "Quality; building" , "Attribute; chattel" , "Asset" .)