To use a filter that has been defined in a plugin, when you can not actually be sure that the plugin is both installed and activated, then you ought not, since SPIP 2.1, call that filter directly ([(#BALISE|specific_function)]), because this will generate a compilation error - instead, you can make a call to the guaranteed installed SPIP standard filter appliquer_filtre:
[(#BALISE|appliquer_filtre{specific_function})].
Any parameters that you would normally pass directly to your specific_function filter can be passed as supplementary parameters instead:
[(#BALISE|appliquer_filtre{specific_function, param1, param2})]