A fibre, a thread, taking an inhalation (6)
I believe the answer is:
breath
'an inhalation' is the definition.
(I've seen this in another clue)
'a fibre a thread taking' is the wordplay.
'taking' indicates the answer is hidden within the clue (the answer is carried or taken by the clue).
'BREATH' is hidden within 'fibre a thread'.
(Other definitions for breath that I've seen before include "An inhalation and exhalation" , "Air drawn in and expelled out" , "Air in an out of the lungs" , "Intake of air" , "Air received and expelled" .)