Goddess seen in pigsties now and again (4)
I believe the answer is:
isis
'goddess' is the definition.
(I've seen this before)
'pigsties now and again' is the wordplay.
'now and again' indicates alternate letters (letters taken on a regular basis).
The alternate letters of 'pigsties' are 'ISIS'.
'seen in' is the link.
(Other definitions for isis that I've seen before include "Egyptian goddess of nature" , "water" , "Oxford's second eight" , "Oxford's second crew" , "Jihadists" .)