One's personal part ribbed all round (6)
I believe the answer is:
thorax
'part ribbed all round' is the definition.
'thorax' can be an answer for 'part' (I have seen 'Part of insect' mean 'thorax' so perhaps 'part' could also mean 'thorax'). I'm not certain of the 'ribbed all round' bit.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for thorax that I've seen before include "Between the neck and belly" , "Part of the human torso between neck and diaphragm" , "Middle section of an insect" , "Part of the body containing 3" , "Middle section of insect's body" .)