South American, extremely sensitive, explains barking dog (6,7)

'dog' is the definition.
(Sussex spaniel is an example)

'south american extremely sensitive explains barking' is the wordplay.
'south american' becomes 'sus' (I've seen this in other clues).
'extremely' means to remove the middle letters.
'sensitive' becomes 'sore' ('sore' can be a synonym of 'sensitive').
'barking' indicates an anagram (UK slang for mad).
'sore' with its centre removed is 'se'.
'explains' is an anagram of 'xspaniel'.
'sus'+'se'+'xspaniel'='SUSSEX SPANIEL'