Become uninhibited and no longer bother about personal appearance (3,7,2)
I believe the answer is:
let oneself go
'become uninhibited and no longer bother' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'personal appearance' is the wordplay.
I cannot quite understand how this works, but
'personal' could be 'ones' (belonging to oneself) and 'ones' is present in the answer.
This explanation may well be incorrect...
'about' acts as a link.
Can you help me to learn more?
(Other definitions for let oneself go that I've seen before include "Act in an uninhibited manner - lose interest in one's appearance" , "Genteel fools (anag) - act without restraint" , "become abandoned" , "Neglect one's appearance" .)