Using a solder with a lower melting point, such as one made of indium, may help to reduce the risk of damaging the fragile THT polystyrene capacitor during the soldering process. However, it is important to ensure that the solder you use is RoHS compliant and suitable for use in a commercial product.
An alternative solution would be to use a larger tip and a more powerful soldering iron. The Hakko FX-951 has a temperature range from 240°C to 540°C, a larger tip may help to distribute the heat more evenly and reduce the risk of damage to the capacitor.
It's also good practice to preheat the PCB before soldering, it will help the heat to dissipate evenly and reduce the risk of damaging the part.
However, it's always a good idea to consult the manufacturer's recommendations for soldering these types of parts and to use the correct soldering techniques and equipment to minimize the risk of damage.