Novice reflected? That’s a good thing (4)
I believe the answer is:
boon
'good thing' is the definition.
(I've seen this in another clue)
'novice reflected?' is the wordplay.
'novice' becomes 'noob' (I've seen this before).
'reflected?' says the letters should be written backwards (letters reflected back).
'noob' backwards is 'BOON'.
'that's a' acts as a link.
(Other definitions for boon that I've seen before include "Godsend" , "Something beneficial - a blessing" , "Favour, request" , "Blessing - sort of companion?" , "A benefit, goes with blessing" .)