Sexually pure son consumed by constant loathing (6)
I believe the answer is:
chaste
'sexually pure' is the definition.
(chaste can mean pure or virginal)
'son consumed by constant loathing' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'consumed by' indicates putting letters inside (inserted letters get consumed).
'constant' becomes 'c' (mathematical abbreviation).
'loathing' becomes 'hate' (loathing is hatred).
'c'+'hate'='chate'
's' put inside 'chate' is 'CHASTE'.
(Other definitions for chaste that I've seen before include "Refraining from sex" , "Sexually virtuous" , "Everlasting" , "Unsullied" , "avoiding relations" .)