Animal's lair beneath end of the garden (4)
I believe the answer is:
eden
'garden' is the definition.
(Garden of Eden in the Bible)
'animal's lair beneath end of the' is the wordplay.
'animal's lair' becomes 'den' (I've seen this before).
'beneath' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'end of' suggests the final letters.
The final letter of 'the' is 'e'.
'den' put after 'e' is 'EDEN'.
(Other definitions for eden that I've seen before include "at Number Ten once?" , "Delightful place" , "Foreign Secretary" , "Need an odd garden?" , "Someone once seen in Number Ten's" .)