Band with a little sibling (5)

I believe the answer is:

oasis

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'band' is the definition.
(British band)

'with a little sibling' is the wordplay.
'with' means one lot of letters go next to another.
'a little' becomes 'oa' (I can't justify this - if you can you should believe this answer much more).
'sibling' becomes 'sis' (short for sister).
'oa'+'sis' is 'OASIS'.

Can you help me to learn more?

(Other definitions for oasis that I've seen before include "Green spot; rock group" , "source of water" , "Place of peace" , "can provide welcome relief" , "Band with Liam and Noel Gallagher" .)

I've seen this clue in The Independent.

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