Chinese currency your aunt regularly used (4)
I believe the answer is:
yuan
'chinese currency' is the definition.
(currency of China)
'your aunt regularly used' is the wordplay.
'regularly used' means one should take alternating letters (letters selected on a regular basis).
'your'+'aunt'='youraunt'
The alternate letters of 'youraunt' are 'YUAN'.
(Other definitions for yuan that I've seen before include "Chinese money" , "Chinese monetary unit" , "Monetary unit of China" , "Chinese currency unit" , "foreign currency" .)