The most common and most likely answer to this crossword clue is the 2 plus 2 letter word IN ON
I've seen this crossword clue in The Times
I
N
O
N
More clues leading to the result IN ON
- Party to open pub with ball...
- Aware of batting side in cricket
- Aware of our originally visiting tavern
- Aware of current refusal from Paris
- Party to duck, held in the local?
- Privy to information, nobody of note initially
- Knowing about home side at The Oval
- Is involved with round within pub
- Privy to remain, one gathers
- Party to end in ennui? Definitely not in Paris
Buddy explains!

The straight part
We know that "Aware of" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case aware of = in 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.