Absence of surprise expressed by ancient mariner (4)
I believe the answer is:
noah
'ancient mariner' is the definition.
(I've seen this in another clue)
'absence of surprise' is the wordplay.
'absence of' becomes 'no'.
'surprise' becomes 'ah' (I can't explain this - if you can you should give a lot more credence to this answer).
'no'+'ah'='NOAH'
'expressed by' acts as a link.
Can you help me to learn more?
(Other definitions for noah that I've seen before include "Biblical patriarch" , "Webster?" , "First collector of animals?" , "Floater" , "Ark-builder" .)