Channel's picture termed incomplete (6)
I believe the answer is:
ureter
'channel's' is the definition.
(ureter is a kind of channel)
'picture termed incomplete' is the wordplay.
'incomplete' indicates the answer is hidden within the clue (an incomplete sample of the clue).
'URETER' is hidden in the letters of 'picture termed'.
(Other definitions for ureter that I've seen before include "wee duct" , "Duct that carries urine" .)