Self-centredness, IMO, gets out of hand (7)
I believe the answer is:
egotism
'self-centredness' is the definition.
(I've seen this before)
'imo gets out of hand' is the wordplay.
'out of hand' indicates an anagram.
'imo'+'gets'='imogets'
'imogets' is an anagram of 'EGOTISM'.
(Other definitions for egotism that I've seen before include "Excessive conceit" , "Obsession with oneself" , "Self-centredness" , "Self-obsession" , "Self-love" .)