Tell what you've seen (6)
I believe the answer is:
report
'tell what you've seen' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for report that I've seen before include "News item - sound of gun" , "Statement of facts, news etc - noise" , "Complain about - account" , "Account, of news say" , "Describe with a bang" .)