Hot water's exciting role with tub (7)
I believe the answer is:
trouble
'hot water's' is the definition.
(I've seen this before)
'exciting role with tub' is the wordplay.
'exciting' indicates anagramming the letters.
'with' says to put letters next to each other.
'role' put after 'tub' is 'tubrole'.
'tubrole' with letters rearranged gives 'TROUBLE'.
(Other definitions for trouble that I've seen before include "Disturb; difficulty" , "Affliction" , "'Care, distress (7)'" , "Anxiety - disturbance - problem" , "Difficulty, problems" .)