Journey down is fair with hint of sun breaking in (7)
I believe the answer is:
Here is my best explanation:
'journey down' is the definition.
(I've seen this before)
'fair with hint of sun breaking in' is the subsidiary indication.
I cannot quite understand how this works, but
'sun' could be 's' and 's' is present in the answer.
'fair' could be 'decent' and 'decent' is present in the remaining letters.
No letters remain.
This may be the basis of clue (or it may be nonsense).
'is' is the link.
(Other definitions for descent that I've seen before include "Lineage", "Downward move", "Bloodline", "Journey down", "Ancestry - downward move", "Downward journey", "A climb down", "Downward slope", "Pedigree" and "Fall".)