Certain to accept surprisingly nice, attractive post (8)
I believe the answer is:
sinecure
'attractive post' is the definition.
(a lucrative job requiring little effort)
'certain to accept surprisingly nice' is the wordplay.
'certain' becomes 'sure' (synonyms).
'to accept' indicates putting letters inside.
'surprisingly' indicates an anagram.
'nice' is an anagram of 'inec'.
'sure' placed around 'inec' is 'SINECURE'.
(Other definitions for sinecure that I've seen before include "Paid job with minimal work - insecure (anag)" , "Post requiring little work" , "Job for easy money" , "Office or job which involvesno work" , "position needing little effort" .)