Son touched by woman doing magic turn (6)
I believe the answer is:
switch
'turn' is the definition.
(I know that switch is a type of turn)
'son touched by woman doing magic' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'touched by' means one lot of letters go next to another.
'woman doing magic' becomes 'witch'.
's'+'witch'='SWITCH'
(Other definitions for switch that I've seen before include "Contact breaker; change" , "Change position" , "Change over - long twig" , "Exchange positions for flexible rod or whip" , "Change or exchange" .)