Callus jerks agitating dog (4,7)
I believe the answer is:
jack russell
'dog' is the definition.
(I've seen this before)
'callus jerks agitating' is the wordplay.
'agitating' indicates anagramming the letters.
'callus'+'jerks'='callusjerks'
'callusjerks' is an anagram of 'JACK RUSSELL'.
(Other definitions for jack russell that I've seen before include "Former England wicketkeeper" , "dog" , "Breed of terrier" , "Small working terrier" .)