Ancient Scottish lord weighed down by gold (4)
I believe the answer is:
auld
'ancient' is the definition.
(thesaurus)
'down by gold' is the wordplay.
'down' becomes 'ld' (I can't explain this - if you can you should believe this answer much more).
'by' means one lot of letters go next to another.
'gold' becomes 'au' (Au is the chemical symbol for gold).
'ld' after 'au' is 'AULD'.
'scottish lord weighed' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for auld that I've seen before include "- - Reekie (Edinburgh)" , "& 11 Song at New Year" , "8" , "& 11 Edinburgh" , "Scots for old" .)