Beautiful operation by a student (4)

I believe the answer is:

opal

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'beautiful operation by a student' is the definition.
I can't tell whether this definition defines the answer.

'operation by a student' is the wordplay.
'operation' becomes 'op'.
'by' means one lot of letters go next to another.
'student' becomes 'l' (as in L-plates for learner drivers).
'op'+'a'+'l'='OPAL'

Can you help me to learn more?

(Other definitions for opal that I've seen before include "National gemstone of Australia" , "Type of gemstone" , "Iridescent gemstone" , "Delicately coloured gem" , "One's stony" .)

I've seen this clue in the Evening Standard.

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