Thinking less than funny? (6)

I believe the answer is:

musing

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

'thinking' is the definition.
(I know that musing is a type of consideration)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for musing that I've seen before include "Reflecting in silence" , "Reflecting or pondering" , "Pondering, thinking" , "introspection" , "Absorbed in thought" .)

I've seen this clue in the Evening Standard.

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