Just one tenor, unattached (6)
I believe the answer is:
adrift
'unattached' is the definition.
Both the definition and answer are adjectives. Maybe there's an association between them I don't understand?
'just one tenor' is the wordplay.
'just one' becomes 'a' (a thing is one thing. I am not sure about the 'just' bit.).
'tenor' becomes 'drift' (drift is a kind of tenor).
'a'+'drift'='ADRIFT'
Can you help me to learn more?
(Other definitions for adrift that I've seen before include "Disoriented" , "(Of ship) out of control" , "Floating freely, not moored" , "'Floating without direction, not tied up (6)'" , "Loose from moorings" .)