Possible Clues:

• Start a conversation
• Get a party going
• Get a delicate dialogue started ... and a hint to 17-, 25-, 34- and 49-Across
• Crack a little joke
• Start a friendship, in a way
• Strike up a conversation, say ... or what five entries in this puzzle do (with a greeting formed by their extra letters!)
• Begin to make (people) relax
• Introduce one's self
• Perhaps get techie to relieve tension
• Overcome unfamiliarity