The most common and most likely answer to this crossword clue is the 6 letter word ONSETS
I've seen this crossword clue in The Daily Telegraph
O
N
S
E
T
S
Buddy explains!
The straight part
We know that "Beginnings" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case beginnings = onsets.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 ONSETS mean?
ONSETS noun- An attack; an assault especially of an army.
- The initial phase of a disease or condition, in which symptoms first become apparent.
- The initial portion of a syllable, preceding the syllable nucleus.
- (acoustics) The beginning of a musical note or other sound, in which the amplitude rises from zero to an initial peak.
- A setting about; a beginning.
- Anything added, such as an ornament or as a useful appendage.
- To assault; to set upon.
- To set about; to begin.