Fools half sorted by the valuer (8)
I believe the answer is:
assessor
'valuer' is the definition.
(thesaurus)
'fools half sorted by' is the wordplay.
'fools' becomes 'asses' (ass is a kind of fool).
'half' indicates taking half.
'by' says to put letters next to each other.
'sorted' with half the letters taken is 'sor'.
'asses'+'sor'='ASSESSOR'
'the' is the link.
(Other definitions for assessor that I've seen before include "One estimates the value of property" , "One who rates for tax" , "One estimating value" , "Insurance valuer" , "One making evaluation" .)