Measuring device capturing old falling star (6)
I believe the answer is:
meteor
'falling star' is the definition.
(synonyms)
'measuring device capturing old' is the wordplay.
'measuring device' becomes 'meter' (device for measuring something, eg a thermometer).
'capturing' means one lot of letters goes inside another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'meter' placed around 'o' is 'METEOR'.
(Other definitions for meteor that I've seen before include "Remote (anag)" , "Body entering earth's atmosphere" , "Remote sort of heavenly body" , "Glowing heavenly body" , "streaker?" .)