Investigations (6)
I believe the answer is:
probes
'investigations' is the definition.
('probe' can be a synonym of 'investigation')
This is all the clue.
(Other definitions for probes that I've seen before include "Examines as dentist does decaying tooth" , "Questions or examines thoroughly" , "Investigates as dentist does tooth" , "Investigates closely" , "Examines carefully as dentist does a bad tooth" .)