The most common and most likely answer to this crossword clue is the 8 letter word MOSQUITO
I've seen this crossword clue in Financial Times
M
O
S
Q
U
I
T
O
More clues leading to the result MOSQUITO
- Ticks abandon old fly
- Fly Ecuadorean capital after some uprising doesn’t end
- Fly low across southern desert
- Fly with squadron leader, stop coming in low
- Bloodsucking insect's low around sierra desert
- Doctors abandon globe to dangerous insect
- The majority almost leave opening of Olivia de Havilland production
- Bloodsucker doctor’s given somewhere in Ecuador
- Parasite’s work pattern very much includes leave
- Buzzer in tiny temple arguably for announcement?
Buddy explains!

The straight part
We know that "Parasite" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case parasite = mosquito.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 MOSQUITO mean?
MOSQUITO noun- A small flying insect of the family Culicidae, the females of which bite humans and animals and suck blood, leaving an itching bump on the skin, and sometimes carrying diseases like malaria and yellow fever.
- To fly close to the ground, seemingly without a course.