Possible Clues:

• Overcome unfamiliarity, in a way
• Start conversation between strangers
• Get social rapport going
• Warm things up, and what 17-, 28- and 50-Across literally do
• Overcome formality
• Make the first move in a conversation
• Begin a conversation, and what the answers to the starred clues do to their circled letters?
• Ease into conversation
• Start a conversation? It's what travellers do in the Arctic
• Initiate cordial conversation, metaphorically