Victor learned to extract uranium for green stones (7)

'green stones' is the definition.
(verdites are green stones)

'victor learned to extract uranium' is the wordplay.
'victor' becomes 'V' (phonetic alphabet: alpha, bravo, charlie etc.).
'learned' becomes 'erudite' (erudite means learned or well-read).
'to extract' suggests deleting specific letters.
'uranium' becomes 'U' (U is the chemical symbol for uranium).
'erudite' with 'u' taken out is 'erdite'.
'v'+'erdite'='VERDITE'

'for' is the link.