Cost adjuster sometimes called "Jimmy" (4)
I believe the answer is:
scot
'called jimmy' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'cost adjuster sometimes' is the wordplay.
'cost' anagrams to 'SCOT'.
However, I'm unsure how the anagram is indicated.
Can you help me to learn more?
(Other definitions for scot that I've seen before include "Eg Aberdonian" , "British northerner" , "Native of Caledonia" , "---- free: originally free from penalties of taxation" , "Glaswegian, say" .)