Article mostly supporting meteorological report (7)
I believe the answer is:
thunder
'meteorological report' is the definition.
(report can mean a loud noise)
'article mostly supporting' is the wordplay.
'article' becomes 'the' (the 'definite article' part of speech).
'mostly' means to remove the last letter.
'supporting' becomes 'under' (a support might be placed under something else).
'the' with its final letter taken away is 'th'.
'th'+'under'='THUNDER'
(Other definitions for thunder that I've seen before include "Atmospheric booms" , "Speak in booming voice" , "Boom; bellow" , "Meteorological rumblings" , "Booming noise after lightning" .)