The average length of a golf club?

It depends on the club. Drivers are the longest clubs - most of them have shafts of around 45". A 3 iron will have a longer shaft than a 4 iron; the clubs get sequentially shorter as the numbers get higher. Putters are the shortest clubs in general, with the exception of belly and long putters. If you are referring to the average length of the Golf clubs in a set, take out your 5 iron and measure that.