Perhaps Galileo's maestro or Newton, possibly (10)
I believe the answer is:
astronomer
'perhaps galileo's' is the definition.
(Galileo was an astronomer)
'maestro or newton possibly' is the wordplay.
'newton' becomes 'N' (symbol for the scientific unit of force).
'possibly' indicates anagramming the letters.
'maestro'+'or'+'n'='maestroorn'
'maestroorn' with letters rearranged gives 'ASTRONOMER'.
(Other definitions for astronomer that I've seen before include "Stargazer" , "Dorado may be contemplated by me" , "Observer of space" , "Star-watcher" , "Space studier" .)