In favour of daughter crossing (4)
I believe the answer is:
ford
'crossing' is the definition.
(synonyms)
'in favour of daughter' is the wordplay.
'in favour of' becomes 'for' (being for a particular cause).
'daughter' becomes 'd' (genealogical abbreviation).
'for'+'d'='FORD'
(Other definitions for ford that I've seen before include "Shallow area in a stream where it can be crossed" , "way for pedestrians" , "Car - river crossing" , "Famous American of yesteryear" , "Place to cross river" .)