Ring us back about the foreign coin (3)
I believe the answer is:
sou
'foreign coin' is the definition.
'sou' can be an answer for 'coin' (sou is a kind of coin). I am not sure about the 'foreign' bit.
'ring us back about' is the wordplay.
'ring' becomes 'o' (letter resembling a ring).
'back' is a reversal indicator.
'about' means one lot of letters goes inside another.
'us' backwards is 'su'.
'o' going within 'su' is 'SOU'.
'the' is the link.
Can you help me to learn more?
(Other definitions for sou that I've seen before include "Former small French coin" , "16 French coin" , "Defunct French coin" , "Former French coin of low value" , "Very little to spend" .)