Meet others in 1009 (3)
I believe the answer is:
mix
'1009' is the definition.
(MIX is 1009 in Roman numerals )
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for mix that I've seen before include "Mingle, blend" , "= 1,009 (L.)" , "Combine into one" , "'Mingle, combine (3)'" , "Blend or socialise" .)