Bovine expert a good many finally dismissed (7)
I believe the answer is:
buffalo
'bovine' is the definition.
(thesaurus)
'expert a good many finally dismissed' is the wordplay.
'expert' becomes 'buff' (I've seen this before).
'good many' becomes 'lot' (a good many can mean a lot).
'finally dismissed' means to remove the last letter.
'lot' with its final letter taken away is 'lo'.
'buff'+'a'+'lo'='BUFFALO'
(Other definitions for buffalo that I've seen before include "Wild ox - New York city" , "Colloquialism for the N American bison" , "Brown bison of North America" , "Horny beast" , "Zoo's inhabitant" .)