Brainbox loses one type (5)
I believe the answer is:
genus
'one type' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for genus that I've seen before include "Taxonomic class between family and species" , "Taxonomic grouping" , "Taxonomic group (biol.)" , "Part of the family" , "Category between family and species" .)