Aussie jumper of grocer worn outside dress, or within (10,4)

'within' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'aussie jumper of grocer worn outside dress or' is the wordplay.
I cannot really see how this works, but
'jumper' could be 'frog' (something which jumps) and 'frog' is found within the answer.
'of' could be 'o' and 'o' is located in the answer.
'or' is found in the answer.
'dress' could be 'robe' (robing is a kind of dressing) and 'robe' is found within the remaining letters.
This explanation may well be incorrect...

Can you help me to learn more?