Sentence:  Other psychoanalytically inspired mother-baby psychotherapeutic approaches, such as that practiced by Serge Lebovici and his colleagues in Paris, freely use the transference as a source of shared clinical focus and as a <WSD>port of entry</WSD> into the system. 
Meaning of the word marked with <WSD> tags:  The location or mechanism by which a foreign entity gains entry into the body or self.