Inspiration again comes in the bath (6)
I believe the answer is:
breath
'inspiration' is the definition.
(thesaurus)
'again comes in the bath' is the wordplay.
'again' becomes 're'.
'comes in' means one lot of letters goes inside another.
're' inserted within 'bath' is 'BREATH'.
(Other definitions for breath that I've seen before include "Air that's inhaled and exhaled" , "An inhalation and exhalation" , "Respiration" , "Intake of air" , "from which inspiration may be drawn" .)