Business site, apparently no longer postponed, encountering obstruction (6,5)
I believe the answer is:
office block
'business site' is the definition.
(building which may contain business premises)
'postponed encountering obstruction' is the wordplay.
'postponed' becomes 'office' (I can't justify this - if you can you should believe this answer much more).
'encountering' means one lot of letters go next to another.
'obstruction' becomes 'block' (block is a kind of obstruction).
'office'+'block'='OFFICE-BLOCK'
'apparently no longer' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for office block that I've seen before include "Large work building" , "Commercial building" , "commercial property" , "Business building" .)