Total number who've paid in gold to get cake (6)
I believe the answer is:
gateau
'cake' is the definition.
(gateau is a kind of cake)
'total number who've paid in gold' is the wordplay.
I cannot really understand how this works, but
'total' could be 'gate' (I have seen 'Total of spectators ' mean 'gate' so perhaps 'total' could also mean 'gate') and 'gate' is located in the answer.
'gold' could be 'au' (Au is the chemical symbol for gold) and 'au' is found within the answer.
No letters remain.
This explanation may well be incorrect...
'to get' acts as a link.
Can you help me to learn more?
(Other definitions for gateau that I've seen before include "Black Forest dessert" , "named for Black Forest?" , "It's sweet" , "(French?) cake" , "Cake for Pierre" .)