Gilbert maybe takes uplifting bath by end of day - ecstasy (8)
I believe the answer is:
rhapsody
'ecstasy' is the definition.
(both can mean a blissful sensation)
'gilbert maybe takes uplifting bath by end of day' is the wordplay.
'gilbert maybe' becomes 'Rhod' (comedian Rhod Gilbert).
'takes' means one lot of letters goes inside another.
'uplifting' is a reversal indicator.
'bath by' becomes 'spa' (I've seen this in another clue. I am not sure about the 'by' bit.).
'end of' suggests the final letters.
The final letter of 'day' is 'y'.
'spa' backwards is 'aps'.
'rhod' placed around 'aps' is 'rhapsod'.
'rhapsod'+'y'='RHAPSODY'
(Other definitions for rhapsody that I've seen before include "Ecstatic statement or romantic musical composition" , "Ecstatic written or romantic musical composition" , "Moving piece of music" , "Emotional musical piece - epic poem" , "Ecstasy" .)