They train dogs (8)
I believe the answer is:
pointers
'dogs' is the definition.
(pointer is a kind of dog)
'they train' is the wordplay.
I cannot quite see how this works, but
'train' could be 'point' (both can mean to aim) and 'point' is found within the answer.
The remaining letters 'ers' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for pointers that I've seen before include "Dogs" , "Clues" , "making a good showing?" , "Tips about proteins" .)