Metal business by Latvian (6)
I believe the answer is:
cobalt
'metal' is the definition.
(cobalt is a kind of metal)
'business by latvian' is the wordplay.
'business' becomes 'co'.
'by latvian' becomes 'balt' (I can't explain this - if you can you should give a lot more credence to this answer).
'co'+'balt'='COBALT'
Can you help me to learn more?
(Other definitions for cobalt that I've seen before include "Metallic element, Co" , "A deep-blue colour (6)" , "Metallic element used in blue/green pigments" , "kind of blue" , "Bright blue pigment" .)