I, on a game, pretended excessive self-importance (8)
I believe the answer is:
egomania
'pretended excessive self-importance' is the definition.
The definition suggests a singular noun which matches the answer.
'i on a game' is the wordplay.
'i on a game' can be anagrammed to 'EGOMANIA'.
But, I am not sure how this is indicated.
Can you help me to learn more?
(Other definitions for egomania that I've seen before include "Abnormally excessive opinion of oneself, quite mad" , "Obsessive self-centredness" , "having no thought for others" , "Feeling very self-conscious" , "selfish obsession" .)