The most common and most likely answer to this crossword clue is the 2 plus 3 plus 4 plus 4 letter word AT THE SAME TIME
I've seen this crossword clue in The Times
A
T
T
H
E
S
A
M
E
T
I
M
E
More clues leading to the result AT THE SAME TIME
Buddy explains!
The straight part
We know that "Simultaneously/however" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case simultaneously/however = at the same time.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.