Turned down or joined up again? (7)
I believe the answer is:
refused
'turned down' is the definition.
('refuse' can be a synonym of 'turn down')
'joined up again?' is the wordplay.
I cannot really see how this works, but
'joined' could be 'fused' (fused means joined together) and 'fused' is found within the answer.
'again?' could be 're' (prefix meaning 'again') and 're' is present in the answer.
No letters remain.
This explanation may well be incorrect...
'or' acts as a link.
Can you help me to learn more?
(Other definitions for refused that I've seen before include "turned down appeal" , "Was unwilling to accept" , "Not accepted" , "Declined, rejected" , "Said no (7)" .)