Investigation moving quickly to snare Stone at last (7)
I believe the answer is:
hearing
'investigation' is the definition.
(hearing is a kind of investigation)
'moving quickly to snare stone at last' is the wordplay.
I cannot quite understand how this works, but
'at' could be 'in' (synonymous in some cases - eg at school, in school) and 'in' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for hearing that I've seen before include "Legal process" , "Trying" , "Her gain (anag.)" , "Perceiving sounds" , "Sense of sound" .)