Datum about European plane (5)
I believe the answer is:
facet
'plane' is the definition.
(facet plane is a kind of plane)
'datum about european' is the wordplay.
'datum' becomes 'fact' (I've seen this before).
'about' means one lot of letters goes inside another.
'european' becomes 'e' (abbreviation e.g. EU).
'fact' placed around 'e' is 'FACET'.
(Other definitions for facet that I've seen before include "Aspect - smooth cut surface" , "Side or surface, diamond or building" , "side of rock" , "Aspect or feature of something" , "(Gem) side; aspect" .)