Unfavourably review list of candidates (5)
I believe the answer is:
slate
This clue is a triple definition!
'unfavourably review' is the first definition.
(slate can mean to criticise harshly)
'list' is the second definition.
(slate is a kind of list)
'of' is a link.
'candidates' is the third definition.
(slate can mean a list of candidates in an election)
(Other definitions for slate that I've seen before include "rock used in building" , "Grey metamorphic rock" , "Blast" , "Bluish-grey colour" , "list of candidates" .)