Mountains containing area around animals (7)
I believe the answer is:
alpacas
'animals' is the definition.
The answer is an example.
'mountains containing area around' is the wordplay.
'mountains' becomes 'alps' (European mountain range).
'containing' indicates putting letters inside.
'area' becomes 'a' (maths abbreviation).
'around' becomes 'ca' (circa).
'a'+'ca'='aca'
'alps' enclosing 'aca' is 'ALPACAS'.
(Other definitions for alpacas that I've seen before include "Llamas with long silky fleece" , "Sources of wool" .)