Base failing, reportedly? (5)
I believe the answer is:
floor
'base' is the definition.
(I know that base can be written as floor)
'failing reportedly?' is the wordplay.
'failing' becomes 'flaw' (I've seen this before).
'reportedly?' indicates a 'sounds like' (homophone) clue (I've seen 'reportedly' mean this).
'flaw' is a homophone of 'FLOOR'.
(Other definitions for floor that I've seen before include "Part of building" , "Fox" , "Bottom surface" , "Sea bottom; baffle" , "Knock down - planking" .)