The most common and most likely answer to this crossword clue is the 4 letter word PREP
I've seen this crossword clue in The Sunday Telegraph
P
R
E
P
More clues leading to the result PREP
- Quiet salesman’s homework
- Homework pages — school subject to be absorbed
- Part of speech, in short, to get ready for theatre
- Go to check king’s ready
- Right to split ginger, chopping food?
- Homework before start of playtime
- Ready pope regarding containment
- Exuberance after securing right kind of school
- Do one’s homework before commencement of project
- Shopping center hosts concerning kind of school
Buddy explains!

The straight part
We know that "Part of speech/to get ready for theatre" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case part of speech/to get ready for theatre = prep.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 PREP mean?
PREP noun- A preventative medical regiment of HIV medicines used to protect against HIV seroconversion after an exposure.
- Preparation.
- A prep school.
- A student or graduate of a prep school, a preppy.
- Homework, work set to do outside class time, used widely in public schools and preparatory schools but not state schools.
- Preparatory level; the last two levels or the fourth and fifth years of preschool; the two levels before first grade.
- To prepare.
- (grammar, strict sense) Any of a class of non-inflecting words typically employed to connect a following noun or a pronoun, in an adjectival or adverbial sense, with some other word: a particle used with a noun or pronoun (in English always in the objective case) to make a phrase limiting some other word.
- A proposition; an exposition; a discourse.