The most common and most likely answer to this crossword clue is the 5 letter word GRINS
I've seen this crossword clue in The Daily Telegraph
G
R
I
N
S
More clues leading to the result GRINS
Buddy explains!

The straight part
We know that "beams" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case beams = grins.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does GRINS mean?
GRINS noun- A smile in which the lips are parted to reveal the teeth.
- To smile, parting the lips so as to show the teeth.
- To express by grinning.
- To show the teeth, like a snarling dog.
- To grin as part of producing a particular facial expression, such as a smile or sneer.
- A snare; a gin.