In any event it's regular (4)
I believe the answer is:
even
I believe this clue is a double definition.
'in any event' is the first definition.
(thesaurus)
'regular' is the second definition.
(similar in meaning)
'it's' is the link.
(Other definitions for even that I've seen before include "draw" , "time when sun goes down for the poet" , "neck and neck" , "Smooth, level" , "Crisp and ---, how King Wenceslas found the snow" .)