Single out car from 1989/90 that's blocking Seat Ateca, essentially (9)
I believe the answer is:
segregate
'single out' is the definition.
(segregating is a kind of singling out)
'that's blocking seat ateca essentially' is the wordplay.
'that' becomes 'greg' (I can't explain this - if you can you should believe this answer much more).
'blocking' is an insertion indicator (to block can mean to plug a gap in something).
'essentially' means to look at the middle letters.
The middle letter of 'ateca' is 'e'.
'greg' placed within 'seat' is 'segregat'.
'segregat'+'e'='SEGREGATE'
'car from 198990' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for segregate that I've seen before include "Isolate, separate" , "Quarantine with easter egg" , "Isolate with Easter Egg" , "Cut off" , "Easter-egg (anag.)" .)