Goad visible, it's said? (6)
I believe the answer is:
incite
'goad' is the definition.
(I know that goad is a more specific form of the action incite)
'visible it's said?' is the wordplay.
'visible' becomes 'insight' (something in sight is visible).
'it's said?' shows a homophone (sound like).
'insight' is a homophone of 'INCITE'.
(Other definitions for incite that I've seen before include "Goad" , "Move to action" , "Urge (to violence)" , "'Stir up, provoke (6)'" , "Provoke to action" .)