Render duet badly but not put off (10)
I believe the answer is:
undeterred
'not put off' is the definition.
(I've seen this before)
'render duet badly' is the wordplay.
'badly' indicates an anagram (letters in the wrong order).
'render'+'duet'='renderduet'
'renderduet' is an anagram of 'UNDETERRED'.
'but' acts as a link.
(Other definitions for undeterred that I've seen before include "without hindrance" , "Not put off" , "going on regardless" , "Nothing daunted" , "Ignoring danger" .)