Grass in class (6)

I believe the answer is:

inform

'grass' is the definition.
(I know that grass is a more specific form of the action inform)

'in class' is the wordplay.
'class' becomes 'form' (synonyms).
'in'+'form'='INFORM'

(Other definitions for inform that I've seen before include "Notify or tell" , "Give information to (someone)" , "snitch?" , "Advise, acquaint with" , "effective" .)

I've seen this clue in The Telegraph.

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