Device I would obtain to prop up top of window (6)
I believe the answer is:
widget
'device' is the definition.
(I know that widget is a type of device)
'i would obtain to prop up top of window' is the wordplay.
'i would' becomes 'I'd'.
'obtain' becomes 'get' (synonyms).
'to prop up' means one lot of letters go next to another.
'top of' says to take the initial letters.
The first letter of 'window' is 'w'.
'id'+'get'='idget'
'idget' put after 'w' is 'WIDGET'.
(Other definitions for widget that I've seen before include "Device used in canned beer" , "Unspecified device" , "Gismo" , "object" , "Useful device for a particular job?" .)