Career over time reveals roots (7)
I believe the answer is:
lineage
'roots' is the definition.
(I've seen this in another clue)
'career over time' is the wordplay.
'career over' becomes 'line' (I can't justify this - if you can you should believe this answer much more).
'time' becomes 'age' (an age is a period of time).
'line'+'age'='LINEAGE'
'reveals' is the link.
Can you help me to learn more?
(Other definitions for lineage that I've seen before include "Genealogy" , "Pedigree, family tree" , "Family descent" , "Descent (from an ancestor)" , "Line of descent or ancestry" .)