Swollen head? Say nothing! (3)
I believe the answer is:
ego
'swollen head?' is the definition.
'ego' can be an answer for 'head?' (ego is a kind of head). I am unsure of the 'swollen' bit.
'say nothing' is the wordplay.
'say' becomes 'eg' (both can mean for example).
'nothing' becomes 'O' (looks like zero - 0).
'eg'+'o'='EGO'
Can you help me to learn more?
(Other definitions for ego that I've seen before include "(Person's) sense of self-esteem" , "Morale" , "Person's sense of self" , "Selfishness" , "Sense of self, conceit" .)