The most common and most likely answer to this crossword clue is the 8 letter word SYRINGES
I've seen this crossword clue in The Daily Telegraph
S
Y
R
I
N
G
E
S
More clues leading to the result SYRINGES
Buddy explains!

The straight part
We know that "medical instruments" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case medical instruments = syringes.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 SYRINGES mean?
SYRINGES noun- A device used for injecting or drawing fluids through a membrane.
- A device consisting of a hypodermic needle, a chamber for containing liquids, and a piston for applying pressure (to inject) or reducing pressure (to draw); a hypodermic syringe.
- A set of panpipes.
- A narrow channel cut in rock, especially in ancient Egyptian tombs.
- The voice organ in birds.
- A rare, fluid-filled neuroglial cavity within the spinal cord or in the brain stem