Sign of virtue from samurai, periodically welcoming new role (7)
I believe the answer is:
aureola
'sign of virtue' is the definition.
(aureola can mean a halo-like circle of light)
'samurai periodically welcoming new role' is the wordplay.
'periodically' indicates alternate letters (letters must be selected 'every so often').
'welcoming' indicates putting letters inside (in sense of 'inviting in').
'new' is an anagram indicator.
The alternate letters of 'samurai' are 'aua'.
'role' with letters rearranged gives 'reol'.
'aua' going around 'reol' is 'AUREOLA'.
'from' acts as a link.
(Other definitions for aureola that I've seen before include "headlight" , "Halo; corona" , "Corona round sun/moon" , "Halo-like form" .)