One without kit frequently found double-dipping a shirt (6)
I believe the answer is:
nudist
'one' is the definition.
Although both the answer and definition are adjectives, I don't see how one could define the other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for nudist that I've seen before include "I lead a bare existence" , "One who disapproves of clothes" , "Person who goes around unclothed" , "He thinks clothes unhealthy" , "Person who believes in going unclothed" .)