The most common and most likely answer to this crossword clue is the 5 letter word ICING
I've seen this crossword clue in The Guardian
I
C
I
N
G
More clues leading to the result ICING
- Decoration here in Paris no good
- Initially it covered immensely nice gateau?
- Decoration that’s partly cosmetic, in general
- Don’t start cutting up top layer of wedding cake
- Spotting, not missing, decorating job
- What's topping individual cakes, including nice gateaux?
- Being a killer contributes to panic in general
- Sweet stuff husband’s culled from Chinese text
- It can top a cake if cream is no good at first
- Topping, terrific in game shows?
Buddy explains!

The straight part
We know that "Topping" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case topping = icing.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ICING mean?
ICING noun- A sweet glaze made primarily of sugar and often flavored, typically used for baked goods; frosting.
- A minor violation of ice hockey rules, occurring when a player shoots the puck from his/her side of the red line so that it crosses the goal line on the opponent's side. A team playing short-handed is not penalized for this.
- The process of forming a layer of ice on a surface.
- To cool with ice, as a beverage.
- To become ice; to freeze.
- To make icy; to freeze.
- To murder.
- To cover with icing (frosting made of sugar and milk or white of egg); to frost; as cakes, tarts, etc.
- To put out a team for a match.
- To shoot the puck the length of the playing surface, causing a stoppage in play called icing.