Oily product in nut tree scattered across Portugal (10)
I believe the answer is:
turpentine
'oily product' is the definition.
(product made from oils from trees)
'in nut tree scattered across portugal' is the wordplay.
'scattered' indicates anagramming the letters.
'across' indicates putting letters inside.
'portugal' becomes 'p' (common abbreviation eg on car number plates).
'in'+'nut'+'tree'='innuttree'
'innuttree' is an anagram of 'turentine'.
'turentine' enclosing 'p' is 'TURPENTINE'.
(Other definitions for turpentine that I've seen before include "Thick, oily resin used as paint thinner" , "Solvent" , "Oil used in varnishes" , "Oil used in mixing paints" , "artist's stuff" .)