A daughter entering before sons and fathers (6)
I believe the answer is:
padres
'fathers' is the definition.
('Padre' can be a synonym of 'father')
'a daughter entering before sons' is the wordplay.
'daughter' becomes 'd' (genealogical abbreviation).
'entering' is an insertion indicator.
'before' becomes 'pre' (prefix meaning 'before').
'sons' becomes 's'.
'a'+'d'='ad'
'ad' put within 'pre' is 'padre'.
'padre'+'s'='PADRES'
'and' acts as a link.
(Other definitions for padres that I've seen before include "Spared as military clergy" , "Army chaplains" , "Fathers" , "Spread (anag.)" , "Spared by clerics" .)