Would-be regicide, chap goes two ways in speech (3,6)
I believe the answer is:
guy fawkes
'would-be regicide' is the definition.
(Guy Fawkes attempted to kill the king)
'chap goes two ways in speech' is the wordplay.
'chap' becomes 'Guy'.
'goes two ways' becomes 'forks' (as in a fork in the road).
'in speech' indicates a 'sounds like' (homophone) clue.
'forks' is a homophone of 'fawkes'.
'guy'+'fawkes'='GUY FAWKES'
(Other definitions for guy fawkes that I've seen before include "His effigy is burned on Nov 5 in England" , "Gunpowder Plot hatcher" , "17th-century conspirator" , "assassin" , "Plotter against James I" .)