basically a comeback, most likely pumped with attitude, sass and or shade.

A dumb-assed replacement phrase for the word-phrase "comeback", which, in normal people English, means "retort".
It makes no sense since "clap" is a word that doesn't represent anything having to do with the meaning of the intention behind the phrase, and meaning something completely different.
In fact, you could replace the verb aspect of this word-phrase with almost any verb, such as:

Fartback
Pushback
Suckback
Blowback
Pickleback
Sayback

and the dumb-assedness of the phrase stays the same, since the focus isn't on it's etymology, but the intention of meaning that the speaker has. The reason that this is dumb is because words mean things and, now, we're arriving at a place where any word can mean anything. This, of course, will inevitably lead to the world simply "barking" at each other like dogs would since, in the future, all we'll need to do is make noises at each other to get our points across since no specific word holds any intrinsic meaning anymore.

To respond to an insult by answering while clapping your hands in rhythm of your words, in order to add empahasis. Common among outraged ghetto women...

When you are that person who thought that what you said was on fleek, but then the person who is 10,000x smarter than you corrected you in the most epic of ways.

If someone roasts you, you have to "clapback" and roast them harder and just come for them, not with violence just with words.

A snarky retort you give to a family member during Thanksgiving, usually in response to a passive aggressive remark made by said family member.

Pelosi Clapback

Applause given to appease someone who does not deserve it, but whose ego desperately needs it. A “Pelosi clapback” can be clearly seen the night of the 2/5/19 POTUS State of the Union address in response to the POTUS suggesting bipartisan cooperation and not realizing the irony. A Pelosi Clapback can be rather sarcastic and very humorous.