I don't see how that would be a problem. They all three should get along just fine without any risk. I take it the clown is a smaller one (e.g. ocellaris) - a bigger more aggressive clown might be a problem in your size tank regardless of how compatible the fish are. Even a maroon would get along with the goby in a suitable tank. (IMO, a maroon in a 29 is not suitable even by itself).
To add: maroons are always risky from what I hear even in large tanks (I won't attempt to ever have one). Depends on the individual fish, but there is quite a few nasty ones out there that don't get along with anything.
Take it with a grain of salt,
I only have personal experience with a few ocellaris in a 75 (they get along fine with everything in there - no wrasse though, just a sand sifting goby and firefish among others which they leave alone), a single clarkii in a 90 and a female and male clarkii in the 180. In the 90 the clarkii doesn't bother the pixie cory wrasse or cross hatch goby and is best buddy with the foxface, but takes no cr*p from the damsels. A couple seargent majors sometimes attempt unsuccesfully to get into her personal space - they run like hell as soon as she makes her move and takes off after them. Same in the 180 - the clowns don't bother the banded goby and pixie cory wrasse, but she defends her anemone to the point of even chasing the male out of it. OTOH, she is smart enough not to mess with the tangs who own the tank (all of it).
Bottom line: mixing clowns, gobies, and wrasses in same tank is less of a concern than adding multiple of each.