Student of the sun, companion welcomed in (7)
I believe the answer is:
scholar
'student' is the definition.
(I know that scholar is a type of student)
'sun companion welcomed in' is the wordplay.
'sun' becomes 'solar' (I've seen this before).
'companion' becomes 'ch' (Companion of Honour).
'welcomed in' is an insertion indicator.
'solar' enclosing 'ch' is 'SCHOLAR'.
'of the' is the link.
(Other definitions for scholar that I've seen before include "Learned (or learning) one" , "Noted academic" , "Pupil - erudite person" , "Student or learned person" , "Distinguished academic" .)