Found squeezing European's heavenly body (6)
I believe the answer is:
planet
'heavenly body' is the definition.
(planet is a type of heavenly body)
'found squeezing european's' is the wordplay.
'found' becomes 'plant' (both can mean to establish).
'squeezing' means one lot of letters goes inside another (inserted letters are squeezed by others).
'european' becomes 'e' (abbreviation e.g. EU).
'plant' enclosing 'e' is 'PLANET'.
(Other definitions for planet that I've seen before include "Orbiting heavenly body" , "Heavenly (or earthly!) body" , "Eg, Mars or Pluto" , "Substantial heavenly body" , "Large satellite of star" .)