Fuss over dubious point for choosing of candidate? (8)
I believe the answer is:
adoption
'choosing of candidate?' is the definition.
(adopting a candidate)
'fuss over dubious point' is the wordplay.
'fuss' becomes 'ado' (synonyms).
'over' means one lot of letters go next to another.
'dubious' indicates anagramming the letters.
'point' anagrammed gives 'ption'.
'ado'+'ption'='ADOPTION'
'for' is the link.
(Other definitions for adoption that I've seen before include "formal selection of candidate?" , "Acceptance (of, eg, a report)" , "Process of taking on another's child" , "Endorsement" , "ratification" .)