Legal tender (5)
'legal tender?' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'tender?' is the wordplay.
I cannot really see how this works, but
'tender?' could be 'nurse' (someone who tends to patients) and 'nurse' is found within the answer.
The remaining letters 'registered' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
'legal tender' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for money that I've seen before include "The 6 [NECESSARY]" , "See 7" , "It's the root of all evil" , "Euro for example" , "Mazuma, ackers or dosh" .)