Sketch unpopular series of descendants (7)
I believe the answer is:
outline
'sketch' is the definition.
(synonyms)
'unpopular series of descendants' is the wordplay.
I cannot quite understand how this works, but
'unpopular' could be 'out' (similar in meaning) and 'out' is present in the answer.
'series' could be 'line' (line is a kind of series) and 'line' is found within the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for outline that I've seen before include "Sketch; summarise" , "General plan; summary" , "Preliminary draft" , "route" , "Preliminary plan or summary of main points" .)