Loners somehow find king inside tube (7)
I believe the answer is:
snorkel
'tube' is the definition.
(thesaurus)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for snorkel that I've seen before include "Breathing pipe for swimmers" , "Tube supplying air to swimmer" , "tube at sea" , "Bent tube for a swimmer's mouth" , "diving equipment?" .)