Border, say, of French brought up (4)
I believe the answer is:
edge
'border' is the definition.
(synonyms)
'say of french brought up' is the wordplay.
'say' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'of french' becomes 'de' ('of' in French).
'brought up' says the letters should be written in reverse (in a down clue, letters go up).
'eg'+'de'='egde'
'egde' back-to-front is 'EDGE'.
(Other definitions for edge that I've seen before include "Move carefully; limit" , "Border; intense quality" , "Final line" , "Rim or slight advantage" , "Intense quality; limit" .)