It may be represented by a tree (7)
I believe the answer is:
lineage
'it may be represented by a tree' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lineage that I've seen before include "The strain" , "Genealogy" , "Descent from ancestors" , "Descent (from an ancestor)" , "Line of descendants of an ancestor" .)