Metal lamp unit is wobbly (8)
I believe the answer is:
platinum
'metal' is the definition.
(I know that platinum is a metal)
'lamp unit is wobbly' is the wordplay.
'is wobbly' is an anagram indicator.
'lamp'+'unit'='lampunit'
'lampunit' is an anagram of 'PLATINUM'.
(Other definitions for platinum that I've seen before include "Precious metal, Pt" , "-- Blonde; -- disc" , "Heavy white metal" , "Valuable substance" , "Silver-white precious metal" .)