Madame, for example, might mention the shape of a gown (4,2,7)
I believe the answer is:
form of address
'a gown' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'madame for example might mention the shape' is the wordplay.
I cannot quite understand how this works, but
'mention' could be 'add' (I've seen this in another clue) and 'add' is located in the answer.
an anagram of 'for' is 'ofr' which is present in the left over letters.
'shape' could be 'form' (synonyms) and 'form' is found within the answer.
The remaining letters 'ess' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'of' is the link.
Can you help me to learn more?