Calms order for seafood (5)
I believe the answer is:
clams
'for seafood' is the definition.
(I've seen this in another clue)
'calms order' is the wordplay.
'order' is an anagram indicator.
'calms' anagrammed gives 'CLAMS'.
(Other definitions for clams that I've seen before include "Their shells are firmly closed" , "Proverbially retentive molluscs" , "Marine bivalves" , "Edible bivalve molluscs" .)