The most common and most likely answer to this crossword clue is the 4 plus 2 letter word ROLL ON
I've seen this crossword clue in Independent
R
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More clues leading to the result ROLL ON
Buddy explains!
The straight part
We know that "I can’t wait" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case i can’t wait = roll on.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.
Crossword Answer definitions
ROLL ON noun- (often in the plural) A type of corset which is rolled on to the body.
- A cosmetic product (especially a deodorant) applied by means of a ball at the head of a container, which rolls the product on to the skin etc.
- (of deodorant, etc.) Applied by means of a ball that can be rotated to pick up liquid from the inner reservoir.