Cook retains right sieve (8)
I believe the answer is:
strainer
'sieve' is the definition.
(thesaurus)
'cook retains right' is the wordplay.
'cook' indicates an anagram.
'right' becomes 'r' (common abbreviation).
'retains' with letters rearranged gives 'straine'.
'straine'+'r'='STRAINER'
(Other definitions for strainer that I've seen before include "Filtering device" , "Kitchen utensil" , "Tea leaf remover" , "one won't let everything go through" , "one that stretches?" .)