Ancestry will produce a row a long time afterwards (7)
I believe the answer is:
lineage
'ancestry' is the definition.
(I know that ancestry can be written as lineage)
'a row a long time afterwards' is the wordplay.
'a row' becomes 'line' (as in a row of things).
'a long time afterwards' becomes 'age' (I've seen this in other clues).
'line'+'age'='LINEAGE'
'will produce' acts as a link.
(Other definitions for lineage that I've seen before include "Family descent" , "Line of descendants of an ancestor" , "Pedigree, family tree" , "The strain" , "Direct descent" .)