Everything has a weight, we hear, at all times (6)
I believe the answer is:
always
'at all times' is the definition.
(synonyms)
'everything has a weight' is the wordplay.
'everything' becomes 'alays' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'has' is an insertion indicator.
'a weight' becomes 'w' (short for weight).
'alays' placed around 'w' is 'ALWAYS'.
'we hear' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for always that I've seen before include "In perpetuity" , "Forevermore" , "For good" , "Evermore" , "On all occasions" .)