Keep watch over son, knowing woman's set on daughter (8)
I believe the answer is:
shepherd
'keep watch over' is the definition.
(thesaurus)
'son knowing woman's set on daughter' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'knowing' becomes 'hep' (alternative to 'hip', which can mean informed).
'woman' becomes 'her' (her refers to a woman).
'set on' is a charade indicator (letters next to each other).
'daughter' becomes 'd' (genealogical abbreviation).
's'+'hep'+'her'+'d'='SHEPHERD'
(Other definitions for shepherd that I've seen before include "One tending a flock" , "Say Corydon" , "working with a crook?" , "Keeper of sheep and goats" , "Flock watcher" .)