Need for a demo, maybe

TNT

Think of a powerful substance often used in controlled explosions, especially in mining or construction—its abbreviation is the same as its full name.

This clue plays on two meanings of "demo." One is short for "demolition," where you might use explosives like TNT. The other is a "demonstration," but the word "maybe" hints that the first meaning is the right path here. The answer is "TNT" because it’s a common explosive used in demolitions, fitting the "need" for blowing things up. The pun relies on the double meaning of "demo" to misdirect slightly before landing on the straightforward answer.