Taxing cash after banks rejected gold put up by America (7)
I believe the answer is:
onerous
'taxing' is the definition.
(I know that taxing can be written as onerous)
'gold put up by america' is the wordplay.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'put' becomes 'eno' (I can't explain this - if you can you should give a lot more credence to this answer).
'up by' is a reversal indicator.
'america' becomes 'US' (United States).
'or'+'eno'='oreno'
'oreno' back-to-front is 'onero'.
'onero'+'us'='ONEROUS'
'cash after banks rejected' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for onerous that I've seen before include "Burdensome as duty may be" , "Heavy and hard to bear" , "Burdensome, demanding" , "Burdensome, taxing" , "Burdensome, oppressive" .)