A narrow beam, perhaps? (5)

I believe the answer is:

smile

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

'beam perhaps?' is the definition.
(beaming is a kind of smiling)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for smile that I've seen before include "express pleasure" , "Show pleasure in slime" , "Visually express amusement" , "Happy facial expression" , "Look happy" .)

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