Foreign money once forged to cover reclaimed tax (7)
I believe the answer is:
centavo
'foreign money' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for centavo that I've seen before include "money abroad" , "(Of games) alternately on one's ground and an opponent's" , "bit of money" , "Mexican coin" , "money overseas" .)