Candidate pairs off with worker (8)
I believe the answer is:
aspirant
'candidate' is the definition.
(thesaurus)
'pairs off with worker' is the wordplay.
'off' indicates anagramming the letters.
'with' is a charade indicator (letters next to each other).
'worker' becomes 'ant' (worker is a type of ant).
'pairs' anagrammed gives 'aspir'.
'aspir'+'ant'='ASPIRANT'
(Other definitions for aspirant that I've seen before include "One works hard to achieve something" , "His desire could make him" , "Hopeful one" , "expressing high ambition?" , "Partisan may be person with high ambition" .)