Flyer beginning to suck one’s blood (6)

I believe the answer is:

siskin

I'm a little stuck... Click here to teach me more about this clue!

'flyer' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.

'beginning to suck one's blood' is the wordplay.
'beginning to' suggests taking the first letters.
'one's' becomes 'is' (Roman numeral).
'blood' becomes 'kin' (I've seen this in another clue).
The first letter of 'suck' is 's'.
's'+'is'+'kin'='SISKIN'

Can you help me to learn more?

(Other definitions for siskin that I've seen before include "Small yellow and black finch" , "Little bird" , "Finch akin to canary" , "Greenish songbird related to Goldfinch" , "Breed of finch" .)

I've seen this clue in The Sunday Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.