Tries other sites occasionally (5)
I believe the answer is:
tests
'tries' is the definition.
(I know this)
'other sites occasionally' is the wordplay.
'occasionally' indicates alternate letters (letters taken at regular intervals or occasions).
'other'+'sites'='othersites'
The alternate letters of 'othersites' are 'TESTS'.
(Other definitions for tests that I've seen before include "Trials for cricketers" , "Examinations, trials" , "Trials -- tribulations" , "Major cricket matches" , "Tries out" .)