Skirt hem easily hides thread (5)
I believe the answer is:
theme
'thread' is the definition.
(thesaurus)
'skirt hem easily hides' is the wordplay.
'hides' says the answer is hidden in the clue.
'THEME' can be found hidden inside 'skirt hem easily'.
(Other definitions for theme that I've seen before include "Short melody" , "thing under discussion" , "Motif that's repeated" , "subject,motif" , "Subject (on which person writes, speaks)" .)