Standard flash measurement used in astronomy (6)
I believe the answer is:
parsec
'measurement used in astronomy' is the definition.
I can't judge whether this defines the answer.
'standard flash' is the wordplay.
'standard' becomes 'par' (standard of play in golf).
'flash' becomes 'sec' (I've seen this in another clue).
'par'+'sec'='PARSEC'
Can you help me to learn more?
(Other definitions for parsec that I've seen before include "Astronomical length - scrape (anag)" , "Measure of distance in space; spacer (anag.)" , "Unit of astronomical length" , "Immense unit of distance" , "Unit for measurement of distance of stars" .)