Check website regularly is on time (4)
I believe the answer is:
test
'check' is the definition.
('test' can be a synonym of 'check')
'website regularly is on time' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'is on' is a charade indicator (letters next to each other).
'time' becomes 't'.
The alternating letters of 'website' are 'est'.
'est' after 't' is 'TEST'.
(Other definitions for test that I've seen before include "Try, examine critically" , "Short exam" , "Analyse" , "Trial - big match" , "Assay" .)