Explained about United's closure (8)
I believe the answer is:
shutdown
'closure' is the definition.
(I know that closure can be written as shutdown)
'explained about united's' is the wordplay.
'explained' becomes 'shown' (I've seen this before).
'about' is an insertion indicator.
'united' becomes 'utd' (common abbreviation as in names of sports teams).
'shown' going around 'utd' is 'SHUTDOWN'.
(Other definitions for shutdown that I've seen before include "Cease business for the day - or permanently" , "Closure" .)