Purser is reeling in shock (8)
I believe the answer is:
surprise
'shock' is the definition.
(I know that shock is a more specific form of the action surprise)
'purser is reeling' is the wordplay.
'reeling' is an anagram indicator.
'purser'+'is'='purseris'
'purseris' with letters rearranged gives 'SURPRISE'.
'in' is the link.
(Other definitions for surprise that I've seen before include "Startle, astonish" , "Sudden unexpected event" , "Shock" , "is not what's expected" , "Astound" .)