He seems surprised by the hors d’oeuvre (7)
I believe the answer is:
starter
'the hors d'oeuvre' is the definition.
(I've seen this before)
'he seems surprised' is the wordplay.
I cannot quite see how this works, but
'he' could be 'arte' and 'arte' is found in the answer.
This may be the basis of clue (or it may be nonsense).
'by' acts as a link.
Can you help me to learn more?
(Other definitions for starter that I've seen before include "First course for beginner" , "No substitute" , "Appetiser" , "Race gun firer" , "One giving signal to begin race" .)