Militant Millicent, reportedly one turned on by Americans (6)
I believe the answer is:
faucet
'one turned on by americans' is the definition.
(US term for a tap)
'militant millicent reportedly' is the wordplay.
'militant millicent' becomes 'fawcett' (women's rights campaigner Millicent Fawcett).
'reportedly' shows a homophone (sound like).
'fawcett' sounds like 'FAUCET'.
(Other definitions for faucet that I've seen before include "North American tap" , "Pipe" , "An American water tap" , "One may turn on this" , "Tap (US)" .)