The most common and most likely answer to this crossword clue is the 4 letter word REED
I've seen this crossword clue in The Daily Telegraph
R
E
E
D
More clues leading to the result REED
- Grass some ungulates rejected
- Ruminants heading north for grass
- Ancient arrow's point, bloodied all around?
- Marsh grass ruminant animal pulled up
- Head of espionage to probe commie grass
- Oliver looking embarrassed about Bumble's finale
- For audience interpret oboe part
- Reportedly study sentence identifying N American singer
- Tall grass in which animals turned up
- Instrument animal knocked over
Buddy explains!

The straight part
We know that "grass" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case grass = reed.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 REED mean?
REED noun- Any of various types of tall stiff perennial grass-like plants growing together in groups near water.
- The hollow stem of these plants.
- Part of the mouthpiece of certain woodwind instruments, comprising a thin piece of wood or metal which shakes very quickly to produce sound when a musician blows over it.
- A musical instrument such as the clarinet or oboe, which produces sound when a musician blows on the reed.
- A comb-like part of a beater for beating the weft when weaving.
- A piece of whalebone or similar for stiffening the skirt or waist of a woman's dress.
- Reeding.
- A tube containing the train of powder for igniting the charge in blasting.
- Straw prepared for thatching a roof.
- A missile weapon.
- A measuring rod.
- To thatch.
- To mill or mint with reeding.
- To become extremely excited; fly into a rage.
- To drive into a state of excitement; fire with enthusiasm.
- To riddle; to sift; to separate or throw off.
- The fourth stomach of a ruminant; rennet.