The cross bolt in the picture ties the tiller to the rudder. That needs to be a really solid connection, with no play whatever. So, yeah, follow Nigel's lead and run a line under the rudder to hold it up, in shallow water
in case you drop the !@#$% rudder and spoil your entire day, disassemble and determine whether the bolt and/or rudder shaft hole is egged. If it is, drill it one size up and install a new stainless steel
The underlying point here is that the ultimate outcome of a loose fit in this situation is having the tiller pull loose from the rudder, ergo no steering
, and it will happen when you apply unusually high force to the tiller, which will already be an OMG moment before you lose steering
. Therefore, it is not a minor annoyance but rather needs a proper repair. Good luck with it.