Unbroken object? Not so (7)
I believe the answer is:
endless
'unbroken' is the definition.
(thesaurus)
'object? not so' is the wordplay.
'object?' becomes 'end' (I've seen this in other clues**).
'not so' becomes 'less' (I've seen this before).
'end'+'less'='ENDLESS'
(Other definitions for endless that I've seen before include "Constant" , "Potentially boring" , "Eternal or interminable" , "without finishing" , "Going on and on, interminable" .)