Archer William to have noticeable effect (4)
I believe the answer is:
tell
This clue could be a double definition.
'archer william' is the first definition.
(I've seen this in another clue)
'have noticeable effect' is the second definition.
'tell' can be an answer for 'have' (thesaurus). I am not certain of the 'noticeable effect' bit.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for tell that I've seen before include "Order" , "Count - recount" , "William ..., skilled Swiss archer" , "Count - give an account" , "blow the whistle" .)