Inform archer (4)
I believe the answer is:
tell
This clue is a double definition.
'inform' is the first definition.
(I know that tell is a more specific form of the action inform)
'archer' is the second definition.
(folk hero William Tell)
(Other definitions for tell that I've seen before include "his hitting the apple?" , "Reveal - command" , "work in a bank" , "Make a difference" , "Rossini composed opera 'William ....'" .)