Drawing back, holding long tube (7)
I believe the answer is:
trachea
'tube' is the definition.
(trachea is a kind of tube)
'drawing back holding long' is the wordplay.
'drawing' becomes 'art' (I've seen this before).
'back' says the letters should be written in reverse.
'holding' means one lot of letters goes inside another.
'long' becomes 'ache' ('ache' can be a synonym of 'long').
'art' in reverse letter order is 'tra'.
'tra' going around 'ache' is 'TRACHEA'.
(Other definitions for trachea that I've seen before include "where air passes" , "air passage" , "airy passage" , "Breathing tube" , "pipe" .)