Inspector very sour for a change (8)
I believe the answer is:
surveyor
'inspector' is the definition.
(thesaurus)
'very sour for a change' is the wordplay.
'for a change' indicates anagramming the letters.
'very'+'sour'='verysour'
'verysour' with letters rearranged gives 'SURVEYOR'.
(Other definitions for surveyor that I've seen before include "Engineer who provides map-making data" , "Land or building measurer" , "Examiner and map-maker of lands and buildings" , "Person who examines the condition of land and buildings" , "One examines" .)