This last sprite, to a smaller extent, is altruistic (8)
I believe the answer is:
selfless
'is altruistic' is the definition.
(synonyms)
'this last sprite to a smaller extent' is the wordplay.
'last' suggests the final letters.
'sprite' becomes 'elf' (an elf is a sprite).
'to a smaller extent' becomes 'less' (I've seen this in other clues).
The last letter of 'this' is 's'.
's'+'elf'+'less'='SELFLESS'
(Other definitions for selfless that I've seen before include "Altruistic" , "Generous" , "Considerate" .)