Object from space encountered below at intervals? Correct, we hear (9)
I believe the answer is:
meteorite
'object from space' is the definition.
(piece of rock from space)
'encountered below at intervals? correct we hear' is the wordplay.
'encountered' becomes 'met' ('meet' can be a synonym of 'encounter').
'at intervals?' indicates alternate letters (I've seen 'at intervals' mean this (letters are taken at regular intervals)).
'correct' becomes 'right' (right can mean correct).
'we hear' indicates a 'sounds like' (homophone) clue.
The alternate letters of 'below' are 'eo'.
'right' sounds like 'rite'.
'met'+'eo'+'rite'='METEORITE'
(Other definitions for meteorite that I've seen before include "Matter in the solar system that reaches earth" , "Something falling from the sky" , "Piece of rock fallen from outer space" , "Lump from space" , "fallen stone" .)