Animal thus inside receptacle (5)
I believe the answer is:
bison
'animal' is the definition.
(I've seen this before)
'thus inside receptacle' is the wordplay.
'thus' becomes 'so' (synonyms).
'inside' indicates putting letters inside.
'receptacle' becomes 'bin' (I've seen this before).
'so' placed into 'bin' is 'BISON'.
(Other definitions for bison that I've seen before include "Large humped bovid of N America" , "Buffalo (US)" , "Buffalo Bill's prey" , "Large shaggy wild ox" , "brute" .)