Selflessness of key game I'm hosting beginning on Saturday (8)
I believe the answer is:
altruism
'selflessness' is the definition.
(synonyms)
'key game i'm hosting beginning on saturday' is the wordplay.
'key' becomes 'alt' (the Alt keyboard button).
'game' becomes 'RU' (rugby union).
'hosting' is an insertion indicator (inserted letters are welcomed in or hosted).
'beginning on' suggests taking the first letters.
The initial letter of 'saturday' is 's'.
'im' going around 's' is 'ism'.
'alt'+'ru'+'ism'='ALTRUISM'
'of' acts as a link.
(Other definitions for altruism that I've seen before include "Unselfish action, generosityfor its own sake" , "Unselfish concern for the welfare of others" , "Unselfishness shown by muralist" , "Unselfishness found in ultraism" , "Selflessness" .)