Fluid source of dance form (3)

I believe the answer is:

tap

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

'dance form' is the definition.
'tap' can be an answer for 'dance' (tapping is a kind of dancing). I am not certain of the 'form' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for tap that I've seen before include "Flow controller; knock" , "Light touch (hot or cold?)" , "Gentle stroke" , "Knock gently" , "In America, it's a spigot" .)

I've seen this clue in The Irish Times.

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