Possible Clues:

• Conforming to accepted notions of propriety
• Proper motor yacht crossing lake south of Norwich, say
• It's only proper to be clever about me getting back with sweetheart
• Becoming wily when penning English, this writer flipped
• Of pleasing appearance
• Socially suitable and polite
• Appropriate to understand, having married fifty years later
• Proper tips from sensible exam lady
• Decent — handsome
• Yes, elm might be suitable