Detection device captures old body in space (6)
I believe the answer is:
meteor
'body in space' is the definition.
'detection device captures old' is the wordplay.
'detection device' becomes 'meter' (device for measuring or detecting something).
'captures' is an insertion indicator.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'meter' enclosing 'o' is 'METEOR'.
(Other definitions for meteor that I've seen before include "A space-traveller" , "Glowing body entering atmosphere" , "it appears as a streak of light" , "Body entering earth's atmosphere" , "Glowing heavenly body" .)