Somewhat obscure regarding US singer and curtailed repeat appearance (9)
I believe the answer is:
recherche
'somewhat obscure' is the definition.
'recherche' can be an answer for 'obscure' (I've seen this before). I am not certain of the 'somewhat' bit.
'regarding us singer and curtailed repeat appearance' is the wordplay.
'regarding' becomes 're' (re can mean regarding, concerning).
'us singer' becomes 'cher' (US musician Cher).
'and' says to put letters next to each other.
'curtailed repeat appearance' becomes 'che' (I can't justify this - if you can you should give a lot more credence to this answer).
're'+'cher'+'che'='RECHERCHE'
Can you help me to learn more?
(Other definitions for recherche that I've seen before include "Rare or far-fetched, like her creche" , "Rare or exotic (French)" , "Rare, exotic, obscure" , "choice" , "Little-known" .)