For one's own part, it sounds vain (4)
I believe the answer is:
vein
'for one's own part it' is the definition.
I can't judge whether this defines the answer.
'sounds vain' is the wordplay.
'sounds' indicates a 'sounds like' (homophone) clue.
'vain' is a homophone of 'VEIN'.
Can you help me to learn more?
(Other definitions for vein that I've seen before include "Rock fissure or minerals therein" , "Distinctive style" , "Part of the blood circulation system" , "part of body" , "Leaf rib; ore layer in rock" .)