Good eggs coming north on road rebuilt for scientist (8)
I believe the answer is:
avogadro
'scientist' is the definition.
(scientist Amedeo Avogadro)
'good eggs coming north on road rebuilt' is the wordplay.
'good' becomes 'g' (abbreviation).
'eggs' becomes 'ova' (term for egg cells).
'coming north' says the letters should be written backwards.
'on' indicates putting letters inside.
'rebuilt' is an anagram indicator.
'g'+'ova'='gova'
'gova' reversed gives 'avog'.
'road' anagrammed gives 'adro'.
'avog' placed inside 'adro' is 'AVOGADRO'.
'for' is the link.
(Other definitions for avogadro that I've seen before include "Italian physicist giving name to a constant" , "Italian gas physicist" , "scientist" .)