Wonderful person from Belgrade accommodating university professor at first (6)
I believe the answer is:
superb
'wonderful' is the definition.
(I know that wonderful can be written as superb)
'person from belgrade accommodating university professor at first' is the wordplay.
'person from belgrade' becomes 'Serb' (Belgrade is the capital of Serbia).
'accommodating' means one lot of letters goes inside another.
'at first' indicates taking the first letters.
The first letters of 'university professor' is 'up'.
'serb' placed around 'up' is 'SUPERB'.
(Other definitions for superb that I've seen before include "Splendid, marvellous" , "Triumphantly effective" , "choice" , "Quite splendid, really excellent" , "fine" .)