Metal bird overturned in a dump uncovered (8)
I believe the answer is:
titanium
'metal' is the definition.
(I know that titanium is a type of metal)
'bird overturned in a dump uncovered' is the wordplay.
'bird' becomes 'tit' (tit is a kind of bird).
'overturned' says the letters should be written backwards.
'uncovered' means to look at the middle letters.
The centre of 'dump' is 'um'.
'in'+'a'='ina'
'ina' reversed gives 'ani'.
'tit'+'ani'+'um'='TITANIUM'
(Other definitions for titanium that I've seen before include "Metallic element used in aircraft components" , "Metal used in strong lightweight alloys" , "Atomic no. 22" , "it's "elementary"" , "Strong light metal, Ti" .)