Pictures likely winners, enthusiastic, on board (9)
I believe the answer is:
snapshots
'pictures' is the definition.
(snapshot is a kind of picture)
'likely winners enthusiastic on board' is the wordplay.
I cannot quite see how this works, but
'likely winners' could be 'naps' (nap can mean a probably winner in a horserace) and 'naps' is found in the answer.
The remaining letters 'shots' 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).
(Other definitions for snapshots that I've seen before include "Informal photos" , "Photographs" .)