Seesaw in local site vandalised (9)
I believe the answer is:
oscillate
'seesaw' is the definition.
(I've seen this before)
'local site vandalised' is the wordplay.
'vandalised' indicates anagramming the letters.
'local'+'site'='localsite'
'localsite' anagrammed gives 'OSCILLATE'.
'in' acts as a link.
(Other definitions for oscillate that I've seen before include "sway" , "Swing between limits" , "Swing to and fro with lost Alice" , "Waver between various options" , "shake" .)