So call in to cook leek (8)
I believe the answer is:
scallion
'leek' is the definition.
(synonyms)
'so call in to cook' is the wordplay.
'to cook' is an anagram indicator.
'so'+'call'+'in'='socallin'
'socallin' with letters rearranged gives 'SCALLION'.
(Other definitions for scallion that I've seen before include "sort of onion" , "Green onion" , "A spring onion with long neck" , "Spring 12" , "Vegetable" .)