A bachelor's is something fundamental (5)

I believe the answer is:

basis

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'fundamental' is the definition.
(thesaurus)

'a bachelor's is' is the wordplay.
'a bachelor's' becomes 'bas' (abbreviation for Bachelor of Arts degree).
'bas'+'is'='BASIS'

'something' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.

Can you help me to learn more?

(Other definitions for basis that I've seen before include "Foundation of a theory or process" , "Principal element" , "Fundamental part" , "Foundation or support, or a main principle" , "Groundwork, foundation" .)

I've seen this clue in the Evening Standard.

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