Rope and long time needed for descent (7)
I believe the answer is:
lineage
'descent' is the definition.
(synonyms)
'rope and long time' is the wordplay.
'rope' becomes 'line' (I've seen this in other clues).
'and' means one lot of letters go next to another.
'long time' becomes 'age' (an age is a period of time).
'line'+'age'='LINEAGE'
'needed for' acts as a link.
(Other definitions for lineage that I've seen before include "Line of descendants of an ancestor" , "Ancestry, sequence of descendants" , "Line of descent or ancestry" , "The strain" , "Ancestral line as seen in eagle" .)