The most common and most likely answer to this crossword clue is the 4 letter word KILL
I've seen this crossword clue in Financial Times
K
I
L
L
Buddy explains!
The straight part
We know that "Waste" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case waste = kill.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 KILL mean?
KILL noun- The act of killing.
- Specifically, the death blow.
- The result of killing; that which has been killed.
- The grounding of the ball on the opponent's court, winning the rally.
- To put to death; to extinguish the life of.
- To render inoperative.
- To stop, cease or render void; to terminate.
- To amaze, exceed, stun or otherwise incapacitate.
- To cause great pain, discomfort or distress to.
- To produce feelings of dissatisfaction or revulsion in.
- To use up or to waste.
- To exert an overwhelming effect on.
- To overpower, overwhelm or defeat.
- To force a company out of business.
- To produce intense pain.
- To punish severely.
- To strike (a ball, etc.) with such force and placement as to make a shot that is impossible to defend against, usually winning a point.
- To cause (a ball, etc.) to be out of play, resulting in a stoppage of gameplay.
- To succeed with an audience, especially in comedy.
- To cause to assume the value zero.
- (IRC) To disconnect (a user) involuntarily from the network.
- To deadmelt.
- (north-east US) A creek; a body of water; a channel or arm of the sea.
- A kiln.