Inspiration about to be found in tub (6)
I believe the answer is:
breath
'inspiration' is the definition.
(thesaurus)
'about to be found in tub' is the wordplay.
'about' becomes 're' (regarding).
'to be found in' means one lot of letters goes inside another.
'tub' becomes 'bath' ('bath' can be a synonym of 'tub').
're' inserted within 'bath' is 'BREATH'.
(Other definitions for breath that I've seen before include "Bather (anag.)" , "It is drawn all the time" , "An inhalation and exhalation" , "Save your ...... - refrain from useless discussion" , "Respiration" .)