Conservative coming in second, being far from reliable (10)
I believe the answer is:
inconstant
'far from reliable' is the definition.
(inconstant can mean unreliable)
'conservative coming in second' is the wordplay.
'conservative' becomes 'con' (abbreviation for Conservative).
'coming in' indicates putting letters inside.
'second' becomes 'instant' (synonyms).
'con' placed into 'instant' is 'INCONSTANT'.
'being' acts as a link.
(Other definitions for inconstant that I've seen before include "Often changing" , "Variable, irregular" , "Fickle" .)