Lock mentioned by quiet fool who will enter unlawfully (8)
I believe the answer is:
trespass
'enter unlawfully' is the definition.
(I've seen this in another clue)
'lock mentioned by quiet fool who' is the wordplay.
I cannot quite see how this works, but
'quiet' could be 'p' (music symbol for 'piano', ie soft or quiet) and 'p' is located in the answer.
'fool' could be 'ass' (both can mean a stupid person) and 'ass' is found in the answer.
The remaining letters 'tres' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'will' is the link.
Can you help me to learn more?
(Other definitions for trespass that I've seen before include "Wrong" , "Enter another's property unlawfully" , "Invade" , "Unlawful entry to someone's property" , "Enter someone's property unlawfully" .)