Dog might be trained someday (7)
I believe the answer is:
samoyed
'dog' is the definition.
(Samoyed is an example)
'trained someday' is the wordplay.
'trained' indicates an anagram (to train can mean to grow something into a shape).
'someday' with letters rearranged gives 'SAMOYED'.
'might be' acts as a link.
(Other definitions for samoyed that I've seen before include "Some day (anag) - dog (from Siberia?)" , "one barking" , "[HOUND] ?" , "Breed of white dog from Siberia - May's ode (anag)" , "not setter!" .)