Short message, not article in Spanish and French (7)
I believe the answer is:
notelet
'short message' is the definition.
(I've seen this before)
'not article in spanish and french' is the wordplay.
'article in spanish' becomes 'el' (I've seen this in other clues).
'and french' becomes 'et' ('and' in French).
'not'+'el'+'et'='NOTELET'
(Other definitions for notelet that I've seen before include "Short folded letter" , "informal communication" , "brief message" , "means of communication" , "Paper for informal letter" .)