It's shown by a person who's retiring (7)
I believe the answer is:
shyness
'it's' is the definition.
I can't judge whether this defines the answer.
'by a person who's retiring' is the wordplay.
'by' says to put letters next to each other.
'a person who's' becomes 'ness' (I can't explain this - if you can you should believe this answer much more).
'retiring' becomes 'shy' (both can mean reserved or introverted).
'ness' put after 'shy' is 'SHYNESS'.
'shown' is the link.
Can you help me to learn more?
(Other definitions for shyness that I've seen before include "Retiring quality" , "Modesty, reticence" , "Reserve" , "lack of confidence" , "Bashfulness" .)