Gold plate shows this, turning up tool (5)
I believe the answer is:
auger
'tool' is the definition.
(auger is a kind of tool)
'gold plate shows this turning up' is the wordplay.
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'plate shows this' becomes 'reg' (a car's reg plate shows its registration number).
'turning up' says the letters should be written in reverse.
'reg' in reverse letter order is 'ger'.
'au'+'ger'='AUGER'
(Other definitions for auger that I've seen before include "Boring instrument" , "Tool for boring holes in wood" , "Boring-tool" , "something that's boring" , "Tool with spiral point for boring" .)