Volunteer adopting traditional dress that's not quite right (3-6)

'not quite right' is the definition.
I don't know anything about this answer so I can't judge whether this works.

'volunteer adopting traditional dress' is the wordplay.
'volunteer' becomes 'offer' (synonyms).
'adopting' indicates putting letters inside (inserted letters are taken on or adopted).
'traditional dress' becomes 'kilt' (I can't justify this - if you can you should give a lot more credence to this answer).
'offer' enclosing 'kilt' is 'OFF-KILTER'.

'that's' acts as a link.

Can you help me to learn more?