Dog needing some sort of protein (7)
I believe the answer is:
pointer
'dog' is the definition.
(I know that Pointer is a dog breed)
'some sort of protein' is the wordplay.
'some sort of' is an anagram indicator.
'protein' with letters rearranged gives 'POINTER'.
'needing' is the link.
(Other definitions for pointer that I've seen before include "under control of mouse" , "Suggestion" , "Hint (for a dog?)" , "Indicator" , "Gun dog" .)