Gratuity possibly given on racecourse (3)
I believe the answer is:
tip
I believe this is a double definition.
'gratuity' is the first definition.
(synonyms)
'possibly given on racecourse' is the second definition.
(as in a betting tip)
(Other definitions for tip that I've seen before include "Pointed end" , "End; piece of advice" , "Hint, suggestion" , "Extremity; gratuity" , "The extreme end of insider information?" .)