Their sister trained a dog (5,6)
I believe the answer is:
irish setter
'a dog' is the definition.
(Irish setter is an example)
'their sister trained' is the wordplay.
'trained' is an anagram indicator (to train can mean to grow something into a shape).
'their'+'sister'='theirsister'
'theirsister' with letters rearranged gives 'IRISH SETTER'.
(Other definitions for irish setter that I've seen before include "Kind of dog" , "Breed of dog" , "best friend" , "Dog from the Emerald Isle" , "Dog with dark red coat" .)