Heaviness caused by delay, say? (6)
I believe the answer is:
weight
'heaviness' is the definition.
(how much something weighs)
'delay say?' is the wordplay.
'delay' becomes 'wait' (synonyms).
'say?' shows a homophone (sound like) (I've seen 'said' mean this).
'wait' sounds like 'WEIGHT'.
'caused by' acts as a link.
(Other definitions for weight that I've seen before include "Burden" , "Relative heaviness" , "The property of heaviness, measure of mass" , "Import" , "Heavy object" .)