Word before "circle" or "tube" (5)
I believe the answer is:
inner
'word before circle or tube' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for inner that I've seen before include "Esoteric" , "Relating to the soul, mind or spirit" , "Located or occurring closer to a centre" , "(Hit on) part of target immediately next to the bullseye" , "Target next to bull" .)