Reportedly delay mass? (6)
I believe the answer is:
weight
'mass?' is the definition.
(I've seen this before)
'reportedly delay' is the wordplay.
'reportedly' indicates a 'sounds like' (homophone) clue.
'delay' becomes 'wait' (synonyms).
'wait' sounds like 'WEIGHT'.
(Other definitions for weight that I've seen before include "Pressure" , "The property of heaviness, measure of mass" , "Burden" , "Relative heaviness" , "Heavy object" .)