Announcer assumes Rechabite is an animal (7)
I believe the answer is:
critter
'an animal' is the definition.
(thesaurus)
'announcer assumes rechabite' is the wordplay.
'announcer' becomes 'crier' (crier is a kind of announcer).
'assumes' indicates putting letters inside.
'rechabite' becomes 'TT' (both can mean a teetotaller).
'crier' enclosing 'tt' is 'CRITTER'.
'is' is the link.
(Other definitions for critter that I've seen before include "Living thing (US)" , "animal in America" , "Creature (American)" , "US beast?" .)