Master's current form (6)

I believe the answer is:

stream

I'm a little stuck... Click here to teach me more about this clue!

'form' is the definition.
(both can mean a group of pupils)

'master's current' is the wordplay.
'master' can be anagrammed to 'STREAM'.
But, I'm unsure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for stream that I've seen before include "group of pupils split by ability" , "Natural body of running water" , "'Brook, runnel (6)'" , "Flock" , "Constant flow of liquid" .)

I've seen this clue in The Irish News and The Globe and Mail.

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