Possible Clues:

• 'Trade discount' quintet
• "Trade discount" quintet
• Quintet to which "Y" may be added
• Sequence contained by the word 'facetious'
• Letters followed by 'and sometimes Y'
• Five vowels
• Ambidextrous features?
• Quintet followed by '... and sometimes Y'
• Gregarious group?
• Group to which 'Y' is sometimes added