Selfishness, for example, over one's millions? (6)
I believe the answer is:
egoism
'selfishness' is the definition.
(I've seen this in another clue)
'example over one's millions?' is the wordplay.
'example' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'over' becomes 'o' (cricket abbreviation).
'one's' becomes 'i's' (Roman numeral).
'millions?' becomes 'm' (abbreviation).
'eg'+'o'+'is'+'m'='EGOISM'
'for' is the link.
(Other definitions for egoism that I've seen before include "Self-centredness, vanity" , "Exaggerated sense of one's own importance" , "Excessive self-regard" , "sense of superiority" , "self-centred doctrine" .)