... where to see punter's tips for Chepstow and Musselburgh? (3)
I believe the answer is:
cam
'where to see punter's' is the definition.
(people punt on the River Cam)
'tips for chepstow and musselburgh?' is the wordplay.
'tips for' suggests taking the first letters (letters at the tips of the words).
The first letters of 'chepstow and musselburgh' is 'CAM'.
(Other definitions for cam that I've seen before include "Projection on a rotating shaft in contact with another part" , "academic stream" , "River also called Granta" , "running into Great Ouse?" , "University city's river" .)