Regularly sleep in, having guaranteed free time (7)
I believe the answer is:
leisure
'free time' is the definition.
(thesaurus)
'regularly sleep in having guaranteed' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'having' is a charade indicator (letters next to each other).
'guaranteed' becomes 'sure' (I've seen this in other clues).
'sleep'+'in'='sleepin'
The alternate letters of 'sleepin' are 'lei'.
'lei'+'sure'='LEISURE'
(Other definitions for leisure that I've seen before include "Free-time" , "R&R" , "Free time; relaxation" , "Rest, relaxation" , "Free time, comfort and convenience" .)