Solid surface, one on a nut (9)
I believe the answer is:
macadamia
'nut' is the definition.
(I've seen this before)
'solid surface one on a' is the wordplay.
'solid surface' becomes 'macadam' (solid surface used on roads).
'one' becomes 'I' (Roman numeral).
'on' means one lot of letters go next to another.
'macadam'+'i'+'a'='MACADAMIA'
(Other definitions for macadamia that I've seen before include "Queensland nut" , "nut-tree" , "(Of drug) causing dependency" , "Australian tree with edible nuts - a CIA madam (anag)" , "Am I a cad, ma? (anag) - Australian nut tree" .)