Possible Clues:

• Take part twirling in dance, social function
• Trig ratio, for short
• Trig ratio (Abbr.)
• Backing group in office social function
• Trigonometrical function of an angle
• 1/sin
• See circle getting tick for ratio
• Function (police social) raised slightly less than half
• Function in trigonometry (abbr)
• Set up in advance, social function