Correspondence from someone who's shy? (10,4)
I believe the answer is:
promissory note
'correspondence' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'from someone who's shy?' is the wordplay.
I cannot really understand how this works, but
'from' could be 'o' (I've seen this in other clues) and 'o' is found within the answer.
'someone' could be 'miss' (miss is a kind of someone) and 'miss' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for promissory note that I've seen before include "marker?" , "Undertaking to repay" , "Financial guarantee" .)