Reliable, faithful (6)
I believe the answer is:
trusty
This clue is a double definition.
'reliable' is the first definition.
(associated in meaning)
'faithful' is the second definition.
(similar in meaning)
(Other definitions for trusty that I've seen before include "Staunch" , "Dependable" , "Reliable, well-behaved prisoners with privileges" , "Reliable, honest and firm" , "Reliable (prisoner)" .)