Possible Clues:

• What student bored at university has that's not at all attractive (7,2,5,4,5)
• Unremarkable boarding pupils, lost for words, may claim to have it (7,2,5,4,5)
• Unremarkable reason for not sending holiday postcard? (7,2,5,4,5)
• Not anything special (7,2,5,4,5)
• Prep school pupil's fear? It's of no special interest (7,2,5,4,5)
• Not very attractive (colloq.) (7,2,5,4,5)
• Unspectacular explanation for blank postcards? (7,2,5,4,5)