Dog in tea garden, barking (5,4)
I believe the answer is:
great dane
'dog' is the definition.
(I know that Great Dane is a type of dog)
'tea garden barking' is the wordplay.
'barking' indicates anagramming the letters (UK slang for mad).
'tea'+'garden'='teagarden'
'teagarden' anagrammed gives 'GREAT DANE'.
'in' is the link.
(Other definitions for great dane that I've seen before include "Hamlet possibly" , "Andersen" , "Could be barking" , "Dog from Copenhagen?" , "A best friend" .)