A little dash can be a bit amusing (5)

I believe the answer is:

minus

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'amusing' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for minus that I've seen before include "Lacking; below zero" , "'Take away' sign" , "Deprived of" , "(Of temperature) below zero" , "Lacking; negative" .)

I've seen this clue in the Evening Standard.

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