Row over time needed for descent (7)
I believe the answer is:
lineage
'for descent' is the definition.
('lineage' can be a synonym of 'descent')
'row over time' is the wordplay.
'row' becomes 'line' (I've seen this before).
'over' is a charade indicator (letters next to each other).
'time' becomes 'age' (age is a kind of time).
'line'+'age'='LINEAGE'
'needed' is the link.
(Other definitions for lineage that I've seen before include "Line of descendants of an ancestor" , "Old family members" , "Ancestry, sequence of descendants" , "Family descent" , "Pedigree, family tree" .)