The most common and most likely answer to this crossword clue is the 4 letter word HAND
H
A
N
D
Buddy explains!

The straight part
We know that "applause" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case applause = hand.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 HAND mean?
HAND noun- The part of the forelimb below the forearm or wrist in a human, and the corresponding part in many other animals.
- That which resembles, or to some extent performs the office of, a human hand.
- In linear measurement:
- A side; part, camp; direction, either right or left.
- Power of performance; means of execution; ability; skill; dexterity.
- An agent; a servant, or manual laborer, especially in compounds; a workman, trained or competent for special service or duty; a performer more or less skillful.
- An instance of helping.
- Handwriting; style of penmanship.
- A person's autograph or signature.
- Personal possession; ownership.
- (usually in the plural, hands) Management, domain, control.
- That which is, or may be, held in a hand at once.
- Applause.
- A Native American gambling game, involving guessing the whereabouts of bits of ivory or similar, which are passed rapidly from hand to hand.
- The small part of a gunstock near the lock, which is grasped by the hand in taking aim.
- A whole rhizome of ginger.
- The feel of a fabric; the impression or quality of the fabric as judged qualitatively by the sense of touch.
- Actual performance; deed; act; workmanship; agency; hence, manner of performance.
- Agency in transmission from one person to another.
- Rate; price.
- To give, pass, or transmit with the hand, literally or figuratively.
- To lead, guide, or assist with the hand; to conduct.
- To manage.
- To seize; to lay hands on.
- To pledge by the hand; to handfast.
- (said of a sail) To furl.
- To cooperate.