Casual about occasionally fraying part of body (6)
I believe the answer is:
larynx
'part of body' is the definition.
'larynx' can be an answer for 'part' (larynx is a kind of part). I am not sure about the 'of body' bit.
'casual about occasionally fraying' is the wordplay.
'casual' becomes 'lax' (I've seen this before).
'about' is an insertion indicator.
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
The alternate letters of 'fraying' are 'ryn'.
'lax' enclosing 'ryn' is 'LARYNX'.
Can you help me to learn more?
(Other definitions for larynx that I've seen before include "Organ containing the vocal cords" , "Location of vocal cords" , "Source of squeaks" , "Human voice box" , "Creator of speech" .)