Prince wearing sexier pants runs out (7)
I believe the answer is:
expires
'runs out' is the definition.
('expire' can be a synonym of 'run out')
'prince wearing sexier pants' is the wordplay.
'prince' becomes 'p' (abbreviation).
'wearing' indicates putting letters inside.
'pants' indicates anagramming the letters (UK informal term for 'nonsense' or 'rubbish').
'sexier' with letters rearranged gives 'exires'.
'p' inserted inside 'exires' is 'EXPIRES'.
(Other definitions for expires that I've seen before include "Comes to the end of allotted time, or dies" , "Breathes out or dies" , "Ends" , "Loses validity; dies" .)