Huge shock! Nostromo alien — can none get lost? (12)
I believe the answer is:
astronomical
'huge' is the definition.
(I've seen this before)
'shock nostromo alien can none get lost?' is the wordplay.
I cannot really see how this works, but
'none' could be 'no' and 'no' is found in the answer.
'lost?' could be 'l' (abbreviation in sporting league tables) and 'l' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for astronomical that I've seen before include "Really, really big" , "Tremendous" , "Extremely large" , "Of the study of stars" , "Inconceivably large" .)