Sun, for example rises, that’s class (5)
I believe the answer is:
genus
'class' is the definition.
(I've seen this before)
'sun for example rises' is the wordplay.
'for example' becomes 'eg' (synonyms).
'rises' shows that the letters should be reversed in order.
'sun'+'eg'='suneg'
'suneg' backwards is 'GENUS'.
'that's' acts as a link.
(Other definitions for genus that I've seen before include "Taxonomic group (biol.)" , "Group of plants with common characteristics" , "Biological group containing one or more species" , "Category between family and species" , "Kind or sort of" .)