Selflessness is founded in key spirit (8)

I believe the answer is:

altruism

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'selflessness' is the definition.
(synonyms)

'founded in key spirit' is the wordplay.
'founded' becomes 'is' (I can't justify this - if you can you should give a lot more credence to this answer).
'in' indicates putting letters inside.
'key' becomes 'alt' (the Alt keyboard button).
'spirit' becomes 'rum' (alcoholic spirit).
'alt'+'rum'='altrum'
'is' inserted into 'altrum' is 'ALTRUISM'.

'is' is the link.

Can you help me to learn more?

(Other definitions for altruism that I've seen before include "Unselfishness shown by muralist" , "Being big" , "Consideration for others first" , "Unselfish action, generosityfor its own sake" , "Unselfishness, Philanthropy" .)

I've seen this clue in The Times.

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