Little animal sent east in a box (4)
I believe the answer is:
cube
'a box' is the definition.
(boxes are cube-shaped)
'little animal sent east' is the wordplay.
I cannot quite see how this works, but
'animal' could be 'cub' (cub is a kind of animal) and 'cub' is present in the answer.
'east' could be 'e' (abbreviation) and 'e' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'in' is the link.
Can you help me to learn more?
(Other definitions for cube that I've seen before include "Solid body with six equal square faces" , "Three dimetional shape" , "For instance, eight" , "Regular 3-D shape" , "Three-dimensional shape with six sides" .)