Conservative girl in charge of son’s great works (8)
I believe the answer is:
classics
'great works' is the definition.
(I've seen this before)
'conservative girl in charge of son's' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'girl' becomes 'lass' (lass can informally mean a girl).
'in charge of' becomes 'ic'.
'c'+'lass'+'ic'+'s'='CLASSICS'
(Other definitions for classics that I've seen before include "great literary works" , "number of races" , "Course" , "Greek and Latin studies" , "horse races" .)