French sea, Italian desert (5)
I believe the answer is:
merit
'desert' is the definition.
(I've seen this before)
'french sea italian' is the wordplay.
'french sea' becomes 'mer' ('sea' in French).
'italian' becomes 'it' (abbreviation for Italian).
'mer'+'it'='MERIT'
(Other definitions for merit that I've seen before include "Good point or quality" , "credit" , "Have a right" , "Excellence that deserves to be honoured" , "Value" .)