Superfluid circulates without drip - that's handy (6)
I believe the answer is:
useful
'that's handy' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for useful that I've seen before include "Very able, competent" , "Utilitarian" , "Beneficial" , "Advantageous; very able" , "Suitable for practical purpose" .)