Pound's confining small animals (6)
I believe the answer is:
beasts
'animals' is the definition.
(I know this)
'pound's confining small' is the wordplay.
I cannot quite see how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is found within the answer.
'pound' could be 'beat' (synonyms) and 'beat' is present in the leftover letters.
A single letter 's' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for beasts that I've seen before include "Fine animals" , "Large four-footed animals or cruel people" , "Creatures; basset (anag.)" , "Basset found among other animals" , "Basest sort of animals" .)