Stargazer loses rag, as it's not as good as the real thing (6)
I believe the answer is:
ersatz
'stargazer loses rag' is the definition.
I can't tell whether this definition defines the answer.
'it's not as good as the real thing' is the wordplay.
I cannot quite understand how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
'real' could be 'e' (e is a kind of real) and 'e' is located in the answer.
'it' could be 'sa' (old-fashioned abbreviation for sex appeal) and 'sa' is found within the answer.
This explanation may well be incorrect...
'as' acts as a link.
Can you help me to learn more?
(Other definitions for ersatz that I've seen before include "Cheap substitute or imitation" , "unnatural" , "Phoney as in Germany" , "Substitute - fake" , "False" .)