Books returned in totally tropical paradise (5)
I believe the answer is:
atoll
'tropical paradise' is the definition.
(I've seen this before)
'books returned in totally' is the wordplay.
'books' becomes 'OT' (abbreviation for Old Testament).
'returned' shows that the letters should be reversed in order.
'in' means one lot of letters goes inside another.
'totally' becomes 'all' (I've seen this in another clue).
'ot' in reverse letter order is 'to'.
'to' placed within 'all' is 'ATOLL'.
(Other definitions for atoll that I've seen before include "String of islands" , "Ring-shaped coral island" , "Bikini, say" , "land threatened by rising sea levels" , "Coral island with central lagoon" .)