Secure area on top of Ukrainian carriage (6)
I believe the answer is:
landau
'carriage' is the definition.
(I've seen this before)
'secure area on top of ukrainian' is the wordplay.
'secure' becomes 'land' (I've seen this in other clues**).
'area' becomes 'a' (maths abbreviation).
'on top of' suggests taking the first letters (I've seen 'on top' mean this).
The initial letter of 'ukrainian' is 'u'.
'land'+'a'+'u'='LANDAU'
(Other definitions for landau that I've seen before include "Old four-wheeled covered carriage" , "Old-fashioned four-wheeled covered carriage" , "Four-wheeled vehicle with two folding hoods" , "An auld type of carriage" , "Four-wheeled horse-drawn carriage" .)