Grow furious -- son's expelled after student looked lecherously (6)

I believe the answer is:

leered

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'looked lecherously' is the definition.
(I've seen this in another clue)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for leered that I've seen before include "Looked lecherously" , "Look suggestively" , "Gazed at lasciviously" , "Looked and smiled lasciviously" , "gave a nasty look" .)

I've seen this clue in The Telegraph.

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