The most common and most likely answer to this crossword clue is the 3 letter word BEG
B
E
G
More clues leading to the result BEG
Buddy explains!

The straight part
We know that "Formally ask" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case formally ask = beg.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 BEG mean?
BEG noun- The act of begging; an imploring request.
- To request the help of someone, often in the form of money.
- To plead with someone for help, a favor, etc.; to entreat.
- In the phrase beg the question: to assume.
- In the phrase beg the question: to raise (a question).
- To ask to be appointed guardian for, or to ask to have a guardian appointed for.
- A provincial governor under the Ottoman Empire; a bey.
- The act of doing that which begins anything; commencement of an action, state, or space of time; entrance into being or upon a course; the first act, effort, or state of a succession of acts or states.
- That which is begun; a rudiment or element.
- That which begins or originates something; the source or first cause.
- The initial portion of some extended thing.