Not so far off, Conservative departing as unsuccessful candidate? (5)
I believe the answer is:
loser
'unsuccessful candidate?' is the definition.
'not so far off conservative departing' is the wordplay.
'not so far off' becomes 'closer' (I've seen this before).
'conservative' becomes 'c' (abbreviation commonly used in UK politics).
'departing' is a deletion indicator.
'closer' with 'c' taken away is 'LOSER'.
'as' acts as a link.
(Other definitions for loser that I've seen before include "Unsuccessful contestant" , "Defeated contestant" , "Defeated person" , "Proverbially, one who hesitates" , "No-hoper" .)