Writer, for example, in building sites (8)
I believe the answer is:
essayist
'writer' is the definition.
(I know that essayist is a type of writer)
'for example in building sites' is the wordplay.
'for example' becomes 'say' ('say' can be used to introduce an example).
'in' is an insertion indicator.
'building' indicates an anagram.
'sites' anagrammed gives 'esist'.
'say' going inside 'esist' is 'ESSAYIST'.
(Other definitions for essayist that I've seen before include "Writer of little prose pieces" , "Writer (e.g. Lamb)" , "Writer of short literary pieces" , "Writer of pieces on various subjects" , "kind of writer" .)