Big entry at Crufts perhaps wrecking tea garden (5,4)
I believe the answer is:
great dane
'big entry at crufts perhaps' is the definition.
(Great Danes are large dogs)
'wrecking tea garden' is the wordplay.
'wrecking' indicates anagramming the letters (I've seen this in other clues).
'tea'+'garden'='teagarden'
'teagarden' anagrammed gives 'GREAT DANE'.
(Other definitions for great dane that I've seen before include "one among best friends" , "Pet" , "Big dog" , "Could be barking" , "Andersen" .)