Extensive extract from popular genealogy (5)
I believe the answer is:
large
'extensive' is the definition.
('large' can be similar in meaning to 'extensive')
'extract from popular genealogy' is the wordplay.
'extract from' says the answer is hidden in the clue (I've seen this in other clues).
'LARGE' is hidden in the letters of 'popular genealogy'.
(Other definitions for large that I've seen before include "Big - 5 down (anag)" , "Tall" , "Above average in size, number, etc." , "Great being regal" , "Immense" .)