Descent with rope possibly taking a long time (7)
I believe the answer is:
lineage
'descent' is the definition.
('lineage' can be a synonym of 'descent')
'rope possibly taking a long time' is the wordplay.
'rope possibly' becomes 'line' (rope is a kind of line**).
'taking' says to put letters next to each other.
'a long time' becomes 'age' ('age' can be a synonym of 'long time').
'line'+'age'='LINEAGE'
'with' is the link.
(Other definitions for lineage that I've seen before include "Descent (from an ancestor)" , "The strain" , "Family descent" , "Direct descent" , "Line of descendants of an ancestor" .)