Do note that it's old-fashioned (5)
I believe the answer is:
passe
'that it's old-fashioned' is the definition.
(I've seen this in another clue)
'do note' is the wordplay.
I cannot really understand how this works, but
'note' could be 'e' (musical note) and 'e' is located in the answer.
The remaining letters 'pass' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for passe that I've seen before include "Past its prime - in France" , "Jaded" , "Master key - picture mounting" , "No longer in fashion" , "Old hat" .)