Serve salad, tossed: it contains capers and anchovies (5,5)
I believe the answer is:
salsa verde
'it contains capers and anchovies' is the definition.
'serve salad tossed' is the wordplay.
'tossed' is an anagram indicator.
'serve'+'salad'='servesalad'
'servesalad' with letters rearranged gives 'SALSA VERDE'.
(Other definitions for salsa verde that I've seen before include "that's saucy" , "spicy foodstuff" , "Italian or Mexican sauce" , "Relish" , "sauce being required" .)