Is surprised when one embarks on (6)
I believe the answer is:
starts
This clue could be a double definition.
'is surprised' is the first definition.
(I've seen this before)
'embarks on' is the second definition.
('start' can be a synonym of 'embark on')
'when one' acts as a link.
I am not very happy about this link. Some or all of it may belong to one of the definitions.
Can you help me to learn more?
(Other definitions for starts that I've seen before include "Begins or makes sudden movement as from surprise" , "Makes sudden movement from pain or surprise" , "Begins or causes to begin" , "Begins to make sudden surprised movements" , "Commences" .)