Regularly tend ferns in famous garden (4)
I believe the answer is:
eden
'famous garden' is the definition.
(I've seen this in another clue)
'regularly tend ferns' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'tend'+'ferns'='tendferns'
The alternating letters of 'tendferns' are 'EDEN'.
'in' acts as a link.
(Other definitions for eden that I've seen before include "Place of unspoiled beauty" , "River - garden" , "Place of complete bliss" , "Delightful place" , "Paradise - ex-PM" .)