Start to don uniform in which one is looking for mate - a classy woman (7)
I believe the answer is:
duchess
'start to don uniform in which one is looking for mate a classy woman' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'start to don uniform in which' is the wordplay.
'start to' indicates taking the first letters.
'in which' becomes 'chess' (I can't justify this - if you can you should believe this answer much more).
The initial letters of 'don uniform' is 'du'.
'du'+'chess'='DUCHESS'
Can you help me to learn more?
(Other definitions for duchess that I've seen before include "title" , "Great lady" , "Wife of a duke" , "Titled female" , "Titled lady" .)