Retiring in quiet year (3)
I believe the answer is:
shy
'retiring' is the definition.
(both can mean reserved or introverted)
'quiet year' is the wordplay.
'quiet' becomes 'sh' ('sh' is used to tell someone to be quiet).
'year' becomes 'y'.
'sh'+'y'='SHY'
'in' acts as a link.
(Other definitions for shy that I've seen before include "Timid; throw quickly" , "Nervous or timid in company" , "Coy" , "Bashful or timid" , "Pitch" .)