ksa is the substitute of cli after the verb śliṣa , when used in the sense of 'embracing'.,
This is a restrictive aphorism. As आश्लिक्षत् कन्याम् 'he embraced the girl'. But समाश्लिषज्जतुकाष्ठम् 'the glue joined the wood'.,
श्लिष आलिङ्गने
Adhyāya 3 · Pāda 1 · Rule 46