Tenor, out of practice, is however reliable (6)
I believe the answer is:
trusty
'reliable' is the definition.
(associated in meaning)
'tenor out of practice' is the wordplay.
'tenor' becomes 't'.
'out of practice' becomes 'rusty' (synonyms).
't'+'rusty'='TRUSTY'
'is however' acts as a link.
(Other definitions for trusty that I've seen before include "Responsible prisoner" , "Reliable, well-behaved prisoners with privileges" , "Dependable" , "Devoted" , "Reliable (prisoner)" .)