Related Clues:

• Last bit of decoration
• H is for icing on the cake
• Fairly good communicating, including good detail ultimately
• Icing on the cake ... or a hint to 20-, 24-, 35- and 43-Across
• Concluding detail, and a feature of 16-, 25-, 37- and 52-Across
• Grace note, and a feature of 20-, 28-, 37- and 46-Across