Golfers must wear clothing (trousers, skirts, shirts, shoes etc) of a type readily available in pros shops and golf retail outlets. That excludes the wearing of denim jeans, tracksuits, beachwear or the like, which are not for sale in golf shops and are not acceptable on a golf course.
In the Clubhouse:
With the exception of smart denim jeans which may now be worn in the Clubhouse, any clothing that is not acceptable on the golf course is similarly not acceptable in the Clubhouse, some events in the clubhouse will still require a specific dress code and members will be informed of that through the notice advertising the event.
Please also note that top coats are not allowed to be draped over the back of chairs in the clubhouse and should instead be stored in the cloak room. It is however permissible to do this with jackets, cardigans.